Journal of Refractive Surgery

Meeting Programs

Abstract

The meetings section in Refractive and Corneal Surgery looks in two directions: the future and the past.

For the future, the Journal will publish the preliminary programs of many societies presenting information on refractive surgery, with special emphasis on the International Society of Refractive Keratoplasty and the European Refractive Surgical Society.

The Journal will also present the programs of recently held meetings, with abstracts and annotations where appropriate. So often, authors present innovative insights, new observations, and substantive data at meetings, but the pressures of everyday life interfere with their publishing these in peer-review journals. To access this information, an ophthalmologist or laboratory worker must attend the meeting, read about it in ophthalmology newspapers, or hear about it from colleagues. Attending meetings is not always possible. News reports written by lay individuals sometimes misinterpret information or allow misrepresentation of the results by the presenter. Communication by word of mouth is spotty at best.

To enhance communication, Refractive and Corneal Surgery, with the support of SLACK Incorporated, will select ophthalmologist-reporters who are attending meetings on refractive surgery. These reporters will provide a copy of the meeting program to be published so that readers can keep abreast of who is talking about what. In addition, the reporters will annotate the meeting, providing summaries of selected papers and surveys of the meeting itself. For the reporter's efforts, SLACK Incorporated will provide an honorarium and a free ophthalmology textbook. This is an excellent incentive for young ophthalmologists and researchers to pay careful attention in the meetings, to provide a service to the refractive surgical community, and to gain a small economic reward.

The reporter will be given a byline in the meeting section and thus will be responsible for the content of what is published, since it will not be submitted to peer review outside the Editorial Board.

If you are interested in serving as a meeting reporter, please contact the Editor. And watch out - the Editor may be contacting you.

First International Conference on Confocal Microscopy and the Second International Conference on 3-D Image Processing in Microscopy

March 15-17. 1989

Academisch Medisch Centerm, in Amsterdam, The Netherlands

Reported by

Barry R. Masters, PhD

Atlanta, Ga

INTRODUCTION AND BACKGROUND

Definition of Confocal Microscopy

What are the applications of confocal microscopy to refractive and corneal surgery? What are the advantages and limitations of confocal imaging systems? What are the limitations of the confocal systems?

The unique feature of the confocal light microscope as compared to the conventional light microscope is the superior depth of field (1.7x better) as well as traverse resolution (0.5x better) that is obtainable. This new technology permits the observation of living tissue with a small depth of focus; the resulting images are high resolution, high contrast and comparable to those made with transmission electron microscopy. This means that the layers of the cornea as well as the subcellular components as well as nerves and cell membranes can be visualized on living tissue. The depth of field of the image in the plane of the cornea can approach 0.2 microns. Outside of this focal plane there is a rapid fall off of intensity, and thus only the object within this plane is visible. There are no light reflections from above and below the plane of focus. In the standard light microscope the out of focus image is blurred; in the confocal microscope the image disappears when it is out of focus.

The basic principles of a confocal imaging system were described in 1961 by Minsky and Figure 1 illustrates the basic principle. The input light from the source and the reflected…

The meetings section in Refractive and Corneal Surgery looks in two directions: the future and the past.

For the future, the Journal will publish the preliminary programs of many societies presenting information on refractive surgery, with special emphasis on the International Society of Refractive Keratoplasty and the European Refractive Surgical Society.

The Journal will also present the programs of recently held meetings, with abstracts and annotations where appropriate. So often, authors present innovative insights, new observations, and substantive data at meetings, but the pressures of everyday life interfere with their publishing these in peer-review journals. To access this information, an ophthalmologist or laboratory worker must attend the meeting, read about it in ophthalmology newspapers, or hear about it from colleagues. Attending meetings is not always possible. News reports written by lay individuals sometimes misinterpret information or allow misrepresentation of the results by the presenter. Communication by word of mouth is spotty at best.

To enhance communication, Refractive and Corneal Surgery, with the support of SLACK Incorporated, will select ophthalmologist-reporters who are attending meetings on refractive surgery. These reporters will provide a copy of the meeting program to be published so that readers can keep abreast of who is talking about what. In addition, the reporters will annotate the meeting, providing summaries of selected papers and surveys of the meeting itself. For the reporter's efforts, SLACK Incorporated will provide an honorarium and a free ophthalmology textbook. This is an excellent incentive for young ophthalmologists and researchers to pay careful attention in the meetings, to provide a service to the refractive surgical community, and to gain a small economic reward.

The reporter will be given a byline in the meeting section and thus will be responsible for the content of what is published, since it will not be submitted to peer review outside the Editorial Board.

If you are interested in serving as a meeting reporter, please contact the Editor. And watch out - the Editor may be contacting you.

First International Conference on Confocal Microscopy and the Second International Conference on 3-D Image Processing in Microscopy

March 15-17. 1989

Academisch Medisch Centerm, in Amsterdam, The Netherlands

Reported by

Barry R. Masters, PhD

Atlanta, Ga

INTRODUCTION AND BACKGROUND

Definition of Confocal Microscopy

What are the applications of confocal microscopy to refractive and corneal surgery? What are the advantages and limitations of confocal imaging systems? What are the limitations of the confocal systems?

The unique feature of the confocal light microscope as compared to the conventional light microscope is the superior depth of field (1.7x better) as well as traverse resolution (0.5x better) that is obtainable. This new technology permits the observation of living tissue with a small depth of focus; the resulting images are high resolution, high contrast and comparable to those made with transmission electron microscopy. This means that the layers of the cornea as well as the subcellular components as well as nerves and cell membranes can be visualized on living tissue. The depth of field of the image in the plane of the cornea can approach 0.2 microns. Outside of this focal plane there is a rapid fall off of intensity, and thus only the object within this plane is visible. There are no light reflections from above and below the plane of focus. In the standard light microscope the out of focus image is blurred; in the confocal microscope the image disappears when it is out of focus.

The basic principles of a confocal imaging system were described in 1961 by Minsky and Figure 1 illustrates the basic principle. The input light from the source and the reflected output to be detected both pass through a pinhole. Only light reflected from the focal plane will pass the pinhole. Since the source and detector pinholes are in equivalent focal planes, the microscope is confocal which means "in focus together". In addition the objective lens is also used two times, for illumination and imaging.

Figure 1: Schematic ray tracing diagram illustrates the principle of the various types of confocal microscopes. A point source of light (formed by the pinhole) is imaged by the lens onto an object plane (the out of focus reflector). The light reflected from the out of focus plane and collected by the lens does not enter the pinhole, and therefore is not detected by the eye or the electronic detector. A scanning system (not illustrated) passes the light beam over the object and an image is formed by the focused rays that do pass through the pinhole. Since the pinhole(s) serve as both a point source and as a point aperture the source and the detector are considered confocal.Figure 2: Basal epithelial cells of the living rabbit cornea show bright cell borders at the level of the cell nucleus. The cells are approximately 30 microns in diameter. Images in Figures 2-4 were made in reflected light using a laser scanning confocal microscope (BioRad) with a Leitz objective of 5Ox, a NA of 1.0. and an illuminating laser of 488 nm.

Figure 1: Schematic ray tracing diagram illustrates the principle of the various types of confocal microscopes. A point source of light (formed by the pinhole) is imaged by the lens onto an object plane (the out of focus reflector). The light reflected from the out of focus plane and collected by the lens does not enter the pinhole, and therefore is not detected by the eye or the electronic detector. A scanning system (not illustrated) passes the light beam over the object and an image is formed by the focused rays that do pass through the pinhole. Since the pinhole(s) serve as both a point source and as a point aperture the source and the detector are considered confocal.

Figure 2: Basal epithelial cells of the living rabbit cornea show bright cell borders at the level of the cell nucleus. The cells are approximately 30 microns in diameter. Images in Figures 2-4 were made in reflected light using a laser scanning confocal microscope (BioRad) with a Leitz objective of 5Ox, a NA of 1.0. and an illuminating laser of 488 nm.

The image is constructed by two methods: either scanning the light beam over the object or scanning the object under the light beam. For observation of living tissues, the preferred choice is to scan the light beam. Two methods are used to accomplish this scanning. Laser scanning systems use a set of vibrating mirrors or solid state devices to scan the light beam and then reconstruct the image on a video screen. Alternatively, a Nipkow disk with many holes 20-100 microns in diameter arranged in an Archimedian spiral is used. In the tandem scanning microscope, the light enters a series of holes on the rotating disk, is reflected off the object, and passes through a series of confocal holes on the other side of the disk. Both sets of holes are confocal. In non-tandem scanning systems, the light from the source and the reflected light pass through the same set of holes. As the disk rapidly rotates the reflected light forms the image as it scans over successive parts of the object.

How does this property of the confocal light microscope relate to the refractive surgeon? The procedures used in refractive surgery involve the creation of a controlled wound, albeit a controlled wound which influences the result of the procedure. Current methods used to study corneal wound healing require the use of several animals which have similar operations and are sacrificed at various times after surgery. Light and electron microscopy are used to construct a time course of the wound healing process. This method incurs considerable time, expense and variability. In contrast, the use of confocal microscopy would allow frequent light microscopic examination of the cornea of a single animal during the course of wound healing - a considerably more parsimonimous approach.

The resolution of the light confocal microscope is such that the following structures are readily imaged: all cells in the epithelial layer, the epithelial basement membrane, Bowman's layer, stromal nerves, stromal keratocytes, Descemets membrane and the fine structure of the endothelial cells (Figures 2-4). Examples of the resolution and contrast obtainable with a laser scanning confocal system are shown in Figures 2-4. A freshly enucleated rabbit eye was imaged with a laser scanning confocal microscope (BioRad) using a Leitz objective of 5OX with an NA of 1.0. The wavelength used was 488 nm, and the images are formed using the reflectance mode.

It is suggested that the in vivo study of Bowman's membrane during the time course of wound healing following refractive surgery would be important in the evaluation of the procedure. Laser refractive surgery may also involve some transient damage to the stromal keratocytes. The time course and the reversal of this damage could easily be studied by the application of confocal microscopy to the stromal region. With this technique it is easy to image the keratocytes and their processes and to document structural changes. The depth and the profile of the incisions made during any type of refractive corneal surgery can be readily measured by confocal microscopy, so that the structural changes in each corneal layer can be studied over time.

Figure 3: Nerve plexus in the anterior stroma imaged in the living rabbit cornea has a branching pattern. The diameter of the nerve fibers is less than one micron. The nuclei of stromal keratocytes are seen in the lower region of the image.Figure 4: Endothelial cells in the living rabbit cornea at the level of the cell nucleus. The cells are about 20 microns in diameter. The light circular regions are the cell cytoplasm; the dark regions are the cell nuclei. The cell borders are not distinct at this focal plane.

Figure 3: Nerve plexus in the anterior stroma imaged in the living rabbit cornea has a branching pattern. The diameter of the nerve fibers is less than one micron. The nuclei of stromal keratocytes are seen in the lower region of the image.

Figure 4: Endothelial cells in the living rabbit cornea at the level of the cell nucleus. The cells are about 20 microns in diameter. The light circular regions are the cell cytoplasm; the dark regions are the cell nuclei. The cell borders are not distinct at this focal plane.

Another potential application is the use of a series of confocal optical sections of the cornea to reconstruct corneal surface topography. Digital image processing techniques could be used to register the serial sections of the cornea, and reconstruct a three dimensional image. In addition, algorithms for the small volume elements comprising the 3-D image (voxels) could be used to study structural changes in the cornea.

Because the confocal microscope sharply rejects out of focus light it is ideal to produce sharp images in the fluorescence mode. The use of fluorescent tagged monoclonal antibodies to specific proteins would have application in the investigation of the role of proteins, other molecules and drugs in the process of corneal wound healing. The role of growth factors in wound repair of the endothelial cells, stromal keratocytes, and basement membrane could be studied in this manner.

The main limitation with the use of in vivo confocal microscopy is the motion of the eye. Several techniques can minimize the effect of the normal motion on the imaging. The first is the use of a suction ring together with an applanation objective lens to stabilize the globe. The second is the use of a flash system to "freeze" the motion of the globe for recording either on film or video, as is widely used for video angiography.

MEETING ORGANIZATION

The combined international congress on confocal microscopy and 3-D image processing in microscopy is an indication of the recent importance of these new developments. While these developments began in the mid-fifties, it was only in the eighties that the availability of less expensive lasers and computers resulted in a blooming of these techniques, especially in the field of computerized tomography and magnetic resonance imaging. The purpose of the joint conference was to bring together these diverse elements in the hope that a helpful cross-fertilization of ideas could take place. This hope was largely fulfilled.

The conference was jointly organized by: The Netherlands Society for Electron Microscopy, The Royal Microscopy society, The International Society for Stereology, and the University of Amsterdam. The Organizing Committee represented the international spirit of the meeting. It consisted of the following members: G.J. Brakenhoff, Amsterdam; A. Boyde, London; V. Howard, Liverpool; A. Kriete, Giessen; W.H. Lamers, Amsterdam; K.D. van der Mast, Delft; N. Nanninga, Amsterdam; J. Smith, Amsterdam; and H.T.M. van der Voort, Amsterdam.

The meeting consisted of oral and poster presentations with ample time for lively discussion as well as excellent working exhibits confocal microscopes and digital image processing systems by: Biorad Laboratories, Utrecht; Sarastro, Stockholm; Tracor Europa B. V., Bilthoven; Wild Leitz B.V., Amsterdam; Zeiss Nederland B. V., Weesp, and others.

SUMMARY OF SELECTED PRESENTATIONS

3-D Imaging of Golgi-Impregnated Neurones using the Tandem Scanning Microscope A. Boyde and M. Freiré Blocks of fixed hamster cerebral cortex were stained by the Golgi-Kopsch method. The Tracor Northern confocal microscope was used to generate a series of images at various degrees of tilt. The 3-D reconstruction program was used to generate stero pairs of images with high contrast and resolution. The details of the cell bodies and the neuronal processes were readily seen in the reconstruction.

Confocal Microscopy, Past, Present and Some Thoughts on the Future

G.J. Brakenhoff

A short review was given on the principle and the optical characteristics of confocal microscopy in various imaging modes. While best known in reflection and fluorescence modes, other modes such as the transmission mode and fluorescence energy transfer to measure molecular distances also have potential. He suggested the use of variable pinholes on both the illumination and the detection paths.

A Confocal Fluorescence Microscope for Digital Recording of Optical Serial Sections

K. Carlsson

A microscope scanner for the automatic recording of stacks of consecutive optical sections has been developed. The specimen remains stationary during scanning, and the laser beam is deflected by scanning mirrors. Instrument performance yields a lateral resolution of 0.3 microns and a depth resolution of 1 micron with an objective of NA 1.3. This instrument is easily modified to incorporate various lasers.

Real-time Confocal Microscopy of the Living Eye

H. Dwight Cavanagh and James V. Jester

They adapted the Tandem Scanning Reflected Light Microscope of Petran and Hadravsky to permit non-invasive, confocal imaging of the living human eye in real-time as recorded by video tape. Optical sections demonstrated the surface epithelial cells, basal epithelial cells, basement membrane, nerve fibers, stromal keratocytes, and endothelial cells. The motion of the eye was apparent in the video images. In addition, they presented slides of in situ rabbit cornea to study the healing response following lamellar- keratectomy and radial keratotomy surgery. They stated that the use of the confocal microscope will fundamentally alter all experimental and clinical approaches to the eye in the future.

A No-Moving-Parts Video Rate Laser Beam Scanning Type 2 Confocal Reflected/Fluorescence Light Microscope

Seth Goldstein

He developed a no-moving parts, 30 frames per second, laser beam scanning confocal microscope suitable for reflection and fluorescence microscopy. The instrument used acoustic-optical modulators to scan the laser beam and an image dissector tube for detection. The main advantage of this system is that many of the aberrations in the optical system of the microscope can be electronically corrected in real-time. In addition, the effective size of the pin-hole and therefore the degree of spatial resolution can be varied electronically. In the reflectance mode the system demonstrated real-time jitter-free images.

Confocal Microscopy of Ocular Tissue

Barry R. Masters

The structure of the cornea of human donor eyes and freshly enucleated rabbit eyes was investigated with a laser scanning confocal microscope. The effects of corneal transparency on the quality of the images and the limits of resolution in the absence of motion of the globe were studied. In addition, the excised retina and the ocular lens were imaged with submicron resolution.

International Symposium on Advanced Refractive and Astigmatism Surgery

April 28-May 1, 1989

Louisville, Ky

Reported by Miles H. Friedlander, MD, New Orleans, LA

The weather in Louisville, Kentucky was ideal, and the excitement was pervasive on the weekend of April 29th - just eight days before the Kentucky Derby. The International Symposium on Advanced Refractive and Astigmatism Surgery, sponsored by the John-Kenyon Eye Research Foundation, was conducted all day Saturday and Sunday. The two course directors, Spencer Thornton and Maurice John, were responsible for organizing this international meeting in which over 40 scientific papers were presented to participants from 22 nations. Highlights from the session are related below.

Management of Astigmatism after Cataract Surgery

Piers Percival, MD, Hutton Buscel, England

Percival emphasized that transverse corneal incisions to correct preexisting astigmatism can only be combined with cataract surgery that uses small incisions or scleral flaps, and not with limbal sections. He places transverse incisions at the 7 mm clear zone and computes one mm in length for every diopter of correction. He prefers to do the transverse cuts before the cataract surgery while the eye is firm and the cornea is undisturbed.

Correction of Astigmatism with Curved or Radial Kerafotomies

Umberto Merlin, MD, Rovigo, Italy

He reviewed his experience with only arcuate transverse incisions with and without radial incisions. At least 0.50 mm should be left between arcuate transverse and the radial incisions to prevent anterior displacement of this tissue bridge. Combined radial and transverse incisions flatten the entire cornea and decrease its overall minus power. There was a general lack of predictability and 20% of eyes required repeated operation. For incisions covering an arc of less than 50°, straight and curved incisions seem to have a similar effect, but for incisions longer than about 50°, the arcuate incisions seem more effective.

Myopic KeratomUeusis'm-Situ

Fernando Navarro, MD, Barcelona Spain

The author emphasized the utility of keratomileusis-insitu. It was difficult to obtain a consistently consistent thickness of the second (refractive) microkeratome cut. He described cases of overcorrected myopic keratomileusis, in which an MKM-in-situ button was used as a keratophakia in a secondary procedure to reduce the overcorrection.

Progressive Hyperopic Shift 8 Years after Radial Keratotomy

Michael. Deitz, MD, Mission, Kansas

This report on á series of approximately 214 eyes involving a metal blade, with follow ups ranging from 96% at 1 year to 7% at 8 years and a series of 519 eyes using a diamond blade with follow ups of 72% at 1 year to 2% at 6 years described the "progressive hyperopia" (continued effect of the surgery) that occurred as a cumulative effect during the 6 to 8 year follow up. The average change in the spherical equivalent for the metal blade cases after 2 years was +0.11 D, after 4 years was +0.46 D, after 6 years was +1.1 D, and after 7 to 8 years was +1.8D. A similar pattern was seen with the diamond knife cases. There was no indication that the progressive hyperopia was slowing down at the 7 to 8 year interval . Between 1 and 6 years after surgery, a continued effect of the surgery of 1 diopter more was observed in 61% of the metal blade cases and 24% of the diamond blade cases. The causes of the progressive hyperopia is unknown.

Surgery for Astigmatism after Corneal Grafts

Silvio Koro, MD, Switzerland

A trapezoidal pattern of semi-radial and transverse incisions was used to correct post keratoplasty astigmatism. The semi-radial incisions did not cross the keratoplasty wound. In a series of 19 eyes, 3 months to 2 years after surgery, for astigmatism of 6 to 9.5 diopters, a 3.5 mm diameter clear zone and transverse incisions 2.5 mm long were used. For astigmatism of 10 to 15 diopters, a 3.0 mm diameter clear zone and transverse incisions 3.5 mm long were used. The residual astigmatism in the lower group was 3.8 ± 2.3 diopters with a 69% overall correction of the initial astigmatism. In the higher group, the residual astigmatism was 3.5 ± 1.75 diopters with an overall correction of 53% at the initial astigmatism. The flattening to steepening ratio was approximately -6.5 to +1.5 diopters.

Stability of Refraction over 4 Years after Radial Keratotomy in the PERK Study

George O. Waring, MD

and the PERK Study Group Atlanta, Georgia

A study of 435 eyes between baseline and 4 years in the PERK study revealed that almost all eyes had a decrease in myopia at 2 weeks after surgery and that almost all eyes showed some loss of this initial effect at 3 months. Between 3 months and 6 months, the refraction stabilized in the majority of the eyes. Between 6 months and 4 years after surgery, 72% of the eyes remained stable, showing Jess than 1 diopter of refractive change; 24% of the eyes showed a continued effect of the surgery (progressive hyperopia) of 1 diopter to approximately 2.5 diopters; only 4% of the eyes showed a loss of effect of the surgery. The number of eyes showing a continued effect of the surgery increased at each annual examination, and there was no suggestion that there was any cessation of this phenomenon at 4 years. Eyes with a smaller diameter clear zone tended to have more continued effect of the surgery.

Correction of Astigmatism

Lee Nordan, MD, La Jolla, CA

The refraction should be displayed in minus cylinder form for proper astigmatism correction. The spherical component should be corrected on the basis of the spherical equivalent of the refraction. The astigmatic component should be corrected as the cylinder component of the refraction. Transverse incisions at approximately 7 mm clear zone diameter are preferred, combined with peripheral radial incisions placed in the steep meridian. The length of the incisions is titrated according to the amount of the astigmatism. For higher amounts of astigmatism, combined semi-radial and non-intersecting transverse incisions (Ruiz procedure) are used. The coupling effect of these incisions must be computed for each case.

Prevention and Management of Surgically Induced Astigmatism

Spencer Thornton, MD, Nashville, TN

Thornton performs a scleral incision for both phacoemulsification and irrigation and aspiration. He prefers either an X-type or continuous suture over interrupted sutures because of the tendency to make them too loose or too tight. He also uses Merselene or Prolene suture instead of nylon, which he feels tends to degrade. In astigmatism against the rule, he waits at least six months before performing a keratotomy, and the patient must have symptoms. He stressed the variability of results and noted that age must be considered in planning the surgical strategy.

The Present Status of Epikeratoplasty

Miles Friedlander, MD, New Orleans, LA

Two companies now supply epikeratoplasty tissue, Allergan Medical Optics (ships its tissue in lyophilized state) and Cryo-optics (tissue delivered in M-K Media). AMO is no longer supplying tissue for myopic epikeratoplasty. Reasons given by AMO were financial plus belief that inlay and only synthetics would dominate in the future. Accuracy remains a major problem: 1/3 to 1/4 of patients are 3 diopters from emmetropia. Indications for epikeratoplasty are monocular adult aphakic patients who are not candidates for secondary implants, aphakia in infants and children who are contact lens intolerant, and contact lens intolerant keratoconus patients with clear corneas and small central to paracentral cones who are not candidates for penetrating keratoplasty.

Indications for Bifocal Implants

Piers Percival, MD, Hutton Buscel, England

In a series of 55 eyes with at least 6 months followup, 70% had an uncorrected visual acuity of 20/40 for distance and J3 for near, but 49% stated that they still needed reading glasses. Blur with small print affected 51%' and 17% could not read J2.

Among the indications are a bifocal IOL in the first eye with normal reading in that eye; a monocular implant in the first eye; monocular cataract in a patient under age 60; and a traumatic cataract in a younger patient. Contraindications include a cataract in the only functioning eye; partial ambylopia, macular degeneration, or any other sight threatening defect.

Aspheric Multifocal Intraocular Lens

Lee Nordan, MD, LA Jolla, CA

Nordan noticed that some post operative refractive surgery patients were able to read well for both distance and near. He felt this phenomenon resulted from surgically induced corneal asphericity. He reasoned that an IOL that is aspheric would create a similar effect without producing astigmatism: the periphery of the lens provides distance vision, while the aspheric paracentral portion corrects for near vision. The patient would not experience diplopia because only one image focuses on the macula at a time. Moreover, the image focused on the macula blocks out all other images.

Pathology and Reliability of the Excimer Laser on the Cornea

Daniele Aron-Rosa, MD, Paris, France

The excimer laser can create narrow and precise linear excisions without marginal thermal damage. In radial keratotomy performed on cadaver eyes, the amount of ablation per pulse was not constant, and the excision depth varied. In part, this may result from the accumulation of debris in the wound. For some unknown reason, both the depth and width of the transverse incisions were more uniform than the radial incisions.

In corneal reprofiling, there was no linear correlation between the ablation per pulse and the number of pulses. The amount of correction has less than anticipated. When Bowman's layer was removed, some patients had clear corneas for 2 years, while others demonstrated subepithelial haze.

Clinically she has successfully treated corneal ulcers and small pterygia with the Excimer. In RK, a template with 8 slits is used. Accuracy of focusing is critical. She estimates that 8 microns of surface ablation are needed for each diopter of correction and that approximately one micron per pulse is removed. Complete removal of residual debris during ablation continues to be a problem and may be responsible for the variability of excision depth.

Computer Assisted Surgical Instrument (CASI)

Howard Straub, MD, Aurora, CO

Straub claims that the CASI increases precision in refractive keratotomies by making incision depth a constant. Corneal thickness is measured and recorded in a computer which glides the blade to a calculated depth - accurate to within ± 2 microns. This system automatically coordinates the depth of the blade with the corneal thickness at any given point, Using a foot pedal, the surgeon may view a graphic color display of both completed and proposed incisions. A voice synthesizer also informs the surgeon of his progress. Both an automatic and a manual mode are available, The blade of the scalpel can be manually advanced or retracted up to 78 steps over incision.

Personal Experience with the Thornton Guide

Harold Stein, MD, Toronto, Ontario

Stein reviewed his 5 year experience with the Thornton Guide. Because it is simple to use and presents very conservative calculations, it makes an ideal tool for the novice. When fitting contact lenses after radial keratotomy, Stein uses the pre-operative K readings and prefers a large diameter lens.

Radial Keratotomy with Four "X" Incisions Plus 4 1/3 Incisions for Low to Moderate Myopia

Canrobert Oliveria, MD, Brazil

With the classic 4-incision RK, there is a high incidence of residual astigmatism caused by two factors: 1) the pressure of the upper lid on the cornea produces an out-pouching at 6 o'clock. 2) the optical center is often superior and the 6 o'clock incision is longer than the others, and therefore has a greater effect.

Additionally, the patient with a classic 4-incision RK has more deformity of the cornea and decreased quality of vision. Oliveria makes a 4 "X" keratotomy with incisions at 45 degrees: 1:30, 4:30, 7:30 and 10:30 o'clock., They are always of equal length. Four additional 1/3 length incisions are placed between the 4 oblique cuts.

He compared the 4 "X" Plus RK in one eye with the standard 8 cut RK in the fellow eye and found that visual acuity, post operative astigmatism, and visual quality were similar in both groups. He has performed the 4 "X" Plus RK on 362 eyes.

Post Operative Treatment of Overcorrection and Undercorrection In RK

Dennis Shepard, MD, Baja, CA

Topical steroids are used in undercorrections to raise the intraocular pressure and to retard wound healing. Initially the instillations of drops ranges from hourly to four times a day depending on the severity of the undercorrection. Timolol is used in overcorrections in hopes that the reduced intraocular pressure will cause a more rapid and greater regression.

The Effect of Collagen Shield Following RK

Robert Marmer, MD, Atlanta, GA

In laboratory studies, the shield was placed in one eye of rabbits with bilateral radial keratotomy. The shield reduced wound gaping and inflammation. On the seventh day, by histological study, a greater number of collagen fibers was found in the eyes with the shield. A preliminary report on 25 patients treated with and without the shield suggested that the eyes with the shield had less edema, earlier stability of refraction, and greater stability at six months than the eyes without the shields. It is possible that a more flattening was obtained with the shield in high myopia.

Eyes with the shield seemed generally more uncomfortable than those just patched. The greatest potential use for the collagen shield is as a drug delivery system.

Use of the Photokeratoscope in Clinical Practice

Miles Friedlander, MD, New Orleans, LA

Friedlander discussed typical findings in post keratoplasty astigmatism with special emphasis on the photokeratoscopic findings in wound dehiscence, which usually occurs in one quadrant. The rings are steep in the periphery and flat as one approaches the center. The central ring often has a tear-drop appearance. Wound revision or wedge resection in the effected quadrant is the treatment of choice; relaxing incisions often fail.

Friedlander also reported on cadaver eye and clinical studies of hexagonal keratotomy. He has modified the current technique in order to eliminate wound gaping and prolonged edema associated with intersecting incisions. Using the cadaver eye as a model, he demonstrated by photokeratoscopic analysis that the modified technique was as effective as the original procedure described by Mendez.

Radial Keratotomy in Myopic Patients with Glaucoma

Antonio Méndez, MD, Baja, CA

Mendez performed RK in six patients (12 eyes) with chronic open angle glaucoma. Their preoperative intraocular pressure ranged from 20 to 28 mm Hg without medication < average 23 mm). Méndez cut from optical zone to the limbus. He takes pachometry measurements 2 mm within the limbus, advances the blade to that reading plus 30 microns, and extends the incisions across the limbus. Ten of the 12 eyes had reduction of IOR Follow-up was from 1 month to 12 months (average 5 months). The pressure ranged from 10 to 16 mm Hg postoperatively. Two eyes had no change in IOR Complications were limbal bleeding at the time of surgery, vascularization and four microperforations where the cuts crossed the limbus.

Backcutting Technique for Undercorrections in RK

Stan Franks, MD, Sydney, Australia

If the optical zone in the original surgery was greater than 3.00 mm, Franks reduces its size by inserting his back cutting blade 2.0 mm peripheral to the original zone mark and cutting centrally to the new, smaller optical zone.

Calculation of Reoperations for Radial Keratotomy

Dennis Shepard, MD, Baja, CA

Shepherd's rule of thumb for the calculation of additional incisions assuming the same knife, the same optical zone and the same incision depth are used, is that each set of 4 new cuts will result in a 10% increase of correction. For example, in a 30-year-old -4.50D myope whose result was -3.50 diopters, four more incisions will reduce the myopic by only 0.35 diopters. Therefore, 12 more incisions would be needed to produce a full diopter of additional correction.

Routine Radial Keratotomy in 1989

Leo Bores, MD, Scottsdale, AZ

In addition to optical zone size, depth of the incision, and age of the patient, Bores feels that scleral rigidity, diameter of the cornea, sex of the patient, and shape of the peripheral cornea are equally important factors for radial keratotomy. Bores has reduced the upper range of correction from -8.00 to - 6.00 diopters. He discontinues soft contact lens wear 48 hours prior to surgery, hard lens 1 week, and orthokeratology 6 months. The depth setting of his diamond blade is based on the average, rather than the thinnest, paracentral readings. His perforation rate is 7%.

Thermokeratoplasty for Hyperopia

Nickolay Pivovorov, MD, Moscow, USSR

A new type of silicone lens implanted in phakic eyes to treat myopia has a collar button shape. The large flange of the lens is seated behind the iris.

Radial thermokeratoplasty is now being called Infrakeratoplasty. Nine hundred patients have had the procedure. Some follow-up spans more than 6 years. As in other refractive keratotomies, the older the patient, the greater the effect. Increased effect is also found in corneas that are thin in the center and thick in the periphery and in corneas with small diameters. The complication rate is still nonexistent.

Keratomileusis in Situ

Luis Ruiz, MD, Bogota, Colombia

Corrections range from 3.5 to 35 diopters. He makes two microkeratome cuts. The first section is about 140 microns thick and 8.5 mm in diameter. A second, more superficial cut is made in the bed. The section is then sutured onto the corneal bed in its unfrozen state. He waits three months after the myopic KM in Situ before performing the astigmatic keratotomy.

Ruiz presented data from two series. In both the preoperative range of myopia was approximately the same. In the first, the average post operative correction was +0.53D ( +6.00 to -7.00). In the second, 94% were within 3 diopters of emmetropia. Both series had a good cluster, but the first series showed a tendency for undercorrection. Astigmatism was unchanged.

Hyperopic correction is performed by making a single microkeratome lamellar excision and suturing the disc of cornea back onto the cornea. The smaller the diameter of the section, the greater the correction. Corrections of up to 6 diopters can be obtained. The disc is 60% to 80% of corneal thickness.

Astigmatic Thermokeratoplasty

Al Neumann, MD, Deland, FL

Neumann and SaIz investigated thermokeratoplasty in cadaver eyes and clinical cases. In the laboratory series they found that the effect was augmented when the number of rays was increased and the diameter of the optical zone was decreased. In clinical studies, endothelial cell loss was not significant. Neumann was concerned about regression, most of which takes place within two months. Long-term data on the duration and extent of correction loss is not yet available. When compared to radial keratotomy, visual recovery is protracted, sometimes requiring 2 to 3 months. Patients experience more discomfort immediately after surgery, and the eyes usually have to be patched for several days. In some cases, thermokeratoplasty with an oval optical zone has been used to reduce astigmatism. Maximum correction is 3 diopters.

The American Experience with Hyperopic Lamellar Keratotomy and Keratomileusis in Situ

Leo Bores, MD, Scottsdale, AZ

Bores reported on 37 cases with an average preoperative myopia of - 18.50 D with a range of - 6.00 to - 22.00 D. Twenty three of the 37 were undercorrected. There was an increase in postoperative astigmatism. Bores has had limited experience with hyperopia. His nine cases were limited to patients who were overcorrected by radial keratotomy. All were at least 6 months post RK.

Because RK tissue is easily sucked up in the microkeratome, the resulting section is too thick. Bores compensates by using a thinner footplate. He states that he has no problems with separation of the radial cuts in either the anterior portion of the cornea or in the recipient bed.

Keratomileusis In Situ - Results of 40 Cases

Ricardo Guimaraes, MD, Belo Horizonte, Brazil

Guimaraes has modified the suturing technique used in keratomileusis in situ. Instead of the traditional running antitork suture, he uses the "BRA" technique, which avoids traction and rotation of the tissue and can be used with irregularly shaped discs. All suturing is performed in the recipient bed, and the sutures are placed over the disc in an hour glass configuration.

Hexagonal Keratotomy for Hyperopia

Antonio Méndez, MD, Baja, CA

Méndez discussed hexagonal keratotomy for hyperopia with and without intersection of the incisions. He uses hexagonal markers of varying diameter for different corrections: 6 mm (1.50D); 5.5mm (2.0 D) and 5.0 mm (3.0D). The variation for each marker is ± 0.75D. In an initial series of 102 eyes performed with connection, 20% had prolonged corneal edema. To avoid connecting incisions, he starts his cut 1 mm outside of the hexagonal marker and stopping 0.5 mm before reaching the apex of the angle. He has performed the modified operation on 14 patients and feels that the results are fairly comparable to the first series: Reduction of hyperopia ranged from +2.00 to +4.25 diopters (mean = +3.07 diopters). Postoperative visual acuity was 20/20 in 80%; 20/30 to 20/40 in the remaining 20%. In six eyes induced astigmatism ranged from 0.50 to -0.75 diopters.

Hexagonal Keratotomy for the Correction of Low Hyperopia

Al Neumann, MD, Deland, Fionda

Neumann reported that 55% of 21 eyes (17 patients) were within 1 diopter of emmetropia. After initial overcorrection, regression occurred at 2 weeks to one month. Stability was complete at six months. Optimum visual acuity was reached fairly slowly. Two cases had prolonged elevation of the edges. He recommended caution in performing this technique.

Ben-Sira Lipschitz Macular Lens

Isaac Lipschitz, MD, Israel

Lipshitz thinks that the corneal asphericity plays an important role in determining the visual acuity in refractive surgery. He has modified a keratotometer in order to take peripheral measurements. Against the rule astigmatism, especially in the superior quadrant, will lead to increased postoperative astigmatism. It is essential to take peripheral corneal measurements in planning the surgery.

Using Blade Technology to Improve RK Results

Maurice John, MD, Jeffersonville, IN

John demonstrated that RK knives from different companies can produce inconsistent results. He recommends that each surgeon use a single company's knife to improve predictability.

Association for Research in Vision and Ophthalmology (ARVO)

Aprii 30-May 5, 1989

Sarasota, FL

Reported by

Osama Ibrahim, MD

The annual meeting of the Association for Research in Vision and Ophthalmology (ARVO) was held in Sarasota, Florida between April 30 and May 5, 1989. Over 4500 physicians and scientists from all over the world gathered in this fantastic small beach town which was all ready for the ARVO members.

People who were there for the first time were amazed by the informality of the meetings and yet the high quality of the scientific content which included almost all fields of clinical and basic research covering 29 topics.

Most of the sessions were specialty-oriented, but there were also a dozen Joint Topic Sessions spaced throughout the week to allow mutual interaction between members of different specialties. Each section had a business meeting for election and internal organization.

The program included four symposia: two of them were of general interest to all members, AIDS and Regulations of Cell Growth while the other two mini symposia were about electrophysiology and eye movements. The program also included a placement service and a small book exhibit. The Social program featured an all-ARVO street party which followed the general symposia while the Section Social house included an informal evening receptions. Clearly, the most important aspect of the meeting was the vigorous discussion among friends engendered by the scientific presentations.

Refractive and Corneal Surgery were covered in more than 100 papers and posters covering refractive keratotomy, lamellar refractive surgery, laser corneal surgery, penetrating keratoplasty, corneal topography and corneal wound healing. We present those about penetrating keratoplasty and epikeratoplasty.

Stability ot Epikeratophakia Over One Year

TL Marvelli, MD, Fort Worth, Tex. TC Prager, PhD, JD Goosey, MD, Hermann Eye Center, Houston, TX

We evaluated the visual stability of 151 myopes and 213 hyperopes, which were broken down to low (<±9.50), medium (±9.50 to ±14.0) or high (>±14.0) pre-existing refractive error groups. There was a total of 85 hyperopes with 12 month follow-up and 123 myopes who had been followed for one year. A multiple Linear regression was performed on median values over time for the two groups with only the low myopia group demonstrating a significant negative slope (p=0.002). The change in spherical equivalent for the low myopes, who were slightly hyperopic at one month post surgery (0.50) and myopic (-0.63) at month 12 was only 1.13 D.

Median uncorrected visual acuity values for both groups appear stable over time and ranged from 20/30 to 20/60. Analyzing median values, hyperopes were approximately two Snellen Lines worse than myopes at 12 months. Cylinder also appeared unaffected over time for both myopes and hyperopes. Hyperopes low and high groups showed a trend towards progression; however, this fell outside of significance. Additional analyses utilizing all data points at each timepoint will be presented. Epikeratophakia appears to be a stable, safe and efficacious procedure for the typical patient, regardless of severity of preexisting refractive error for both myopes and hyperopes.

Comment: The authors also reported a two-year follow-up in 54 eyes done by three surgeons. They showed that 60% of cases were 20/40 or better and that 90% of cases were within ±1.0 D. They concluded that variability of refraction occurs between 6, 8, 12 months and unlike other studies they reported that only two patients show >1 D of change between one and two years.

Epithelial Barrier Function After Epikeratophakia

M Busin and M Spitznas. University Eye Hospital, Bonn, Federal Republic of Germany.

Morphologic changes in the corneal epithelium have been described up to 16 months after epikeratophakia. In a prospective study we have investigated the barrier function of the corneal epithelium in 23 adult patients preoperatively and at various times (1, 2, 4, 8, 12, 26, and 52 weeks) after surgery by means of fluorophotometry. Followup data after 12 weeks are available for all 23 patients; 26 and 52 weeks after surgery values were obtained for 13 and 7 patients respectively. The concentration of fluorescein in the corneal stroma 45 min. after application of 20 µ? of a 2% fluorescein solution was measured by means of the Coherent Radiation Fluorotron Master. A statistically significant increase (p<0.05, paired Student's t-test) in stromal fluorescein concentration was recorded both 1 and 2 weeks after epikeratophakia. However, as soon as 4 weeks after surgery no more significant increase was found. Starting at 8 weeks following surgery, a statistically significant reduction in stromal fluorescein concentration was seen (p<0.05). The average concentration of fluorescein in the corneal stroma 45 min. after topical application ranged from 301.9 ± 232.9 ng/ml to a maximum of 1765.4 ± 1350.3 ng/ml 1 week after surgery, and a minimum of 115.9 ± 61.6 ng/ml 52 weeks after surgery.

Comment: Out of the 23 adults, 13 eyes had keratectomy (keratoconus) while 10 eyes had no keratectomy and all eyes were completely epithelial ized after six days.

Myopic Epf keratoplasty - 12 Month Evaluation on 60 Procedures

JD Goosey, TC Prager, Dl Martin and CB Goosey, Department of Ophthalmology, University of Texas Medical School, Houston, TX

As of August 31, 1988, 13 surgeons had performed 136 myopic epikeratoplasties (MEK) on 93 patients. Sixteen patients, 12%, had bilateral surgery. One hundred fourteen of the MEKs had a single procedure, while 11 underwent a repeat surgery. At 12 months post-surgery there was a total of 80 single procedures and nine repeat MEK's. The mean preoperative best corrected visual acuity was 20/31 (20 SD), median 20/20. These values were essentially unchanged at month 12 (mean 20/32, 17 SD; median 20/25). Of those patients who had a preoperative best corrected visual acuity of 20/40 or better, 56% had 20/40 or better uncorrected visual acuity at 12 months. Eighty-nine percent of the single procedure population were 20/100 or better. An analysis of spherical equivalents at 12 months demonstrated that 41% (33/80) were within 1 diopter of emmetropia, 65%, were within 2 diopters and 75% were within 3 diopters. The majority (8/9) of the repeat procedures had 20/60 uncorrected vision and all were correctable to within two Snellen lines of their preoperative best corrected vision. Several significant factors which can affect long-term results, including the age of the patient, depth of trephination, and keratotomy/keratectomy will be discussed.

Comment: He reported 103 patients whose mean age 30.8 years, and they had 147 procedures with 19% having repeated operations. He stressed the effect of trephination depth on outcome.

Twelve Month Followup and Histology of Standard (Freeze/LyophilizedJ and Non-Freeze (BKS-1000) Human Epikeratophakia Tissue Lenses in Monkeys

G Stephenson, B Salmerón, M McDonald, R Beuerman, H Kaufman. LSU Eye Center, New Orleans, LA

Eight pairs of human donor corneas were used to prepare 8 pairs of tissue lenses, 1 non-freeze and 1 standard from each pair; each pair was shaped to correct the same amount of myopia, either 13.5D or 20.5D. Eight monkeys received one pair each (N=16). Self-induced trauma (2 eyes) and late stromal haze/melting (4 eyes) required removal of 3 tissue lenses of each type. In the first 3 months (N=IO), the nonfreeze tissue lenses had greater clarity, after which the two types were equally clear. At 3, 6, 9, and 12 months, the power of the tissue lenses was of equal predictability for both types of preparation and in both the 13.5D and 20.5D groups. At 12 months, two non-freeze and two standard lenses were obtained by PKP for histology. The non-freeze tissue was found to have essentially normal morphology. The freeze/lyophilized lenses showed scattered areas of fracture/absence of Bowman's layer, abnormal keratocytes, irregular distribution of keratocyte repopulation, and anterior stromal lacunae. Also, the non-freeze tissue demonstrated evenly distributed keratocytes without persistent fibroblastic cells, while the standard lenses demonstrated anteriorly located fibroblasts just beneath the surface of the lens, and disruption of Bowman's layer. These results indicate that non-freeze lenses have normal morphology, which may account for the earlier achievement of tissue lens clarity in the primate eye.

Supported in part by PHS grants EY03635, EYO2580, EYO4074, and EY02377.

Comment: He stressed that non-freeze tissue was better than lyophilized tissue as it cleared faster.

Unfrozen Epikeratophakia Grafts Do Not Elicit Allograft Reactions

JM Frantz, BM Gebhardt, G Stephenson, and MB McDonald, LSU Eye Center, New Orleans, LA

The BKS-1000 technique was introduced as a means of preparing epikeratophakia tissue lenses without the need for cryolathing or lyophilization. The objective of this study was to determine if immune graft rejection can be induced by unfrozen epikeratophakia lenses in donor-sensitized rabbits. Fourteen rabbit eyes underwent epikeratophakia. Each animal received tissue lenses from donor rabbits to which they had been previously sensitized by six injections of blood leukocytes given at two week intervals. Five animals also received donor skin grafts. Serum cytotoxic antibody assays were performed prior to surgery to confirm that each recipient had been sensitized to donor histocompatibility antigens. Seven eyes received cryolathed and lyophilized tissue lenses; none developed infiltrates, vascularization, or rejection lines characteristic of stromal allograft rejections. Seven eyes received unfrozen epikeratophakia tissue lenses; one became vascularized and opaque. Six remained clear and appeared identical to the lyophilized lenses. Neither lyophilized tissue lenses nor unfrozen epikeratophakia lenses elicit immune graft reactions in specifically sensitized recipients. Thus, the use of fresh, unfrozen epikeratophakia lenses in humans should not pose immunologic problems.

Supported in part by USPHS grants EYO6094, EYO3150, and EY03635.

Comment: The only case of failure which was vascularized and opaque showed only P.N.LS and no lymphocytes thus excluding an allograft reaction and suggesting a toxic delayed technical fault.

Immunohlstochemistry of Moist-Pak Epikeratophakia Tissue Lenses in Primates

DHKang, MB McDonald, F Amirpanahi, B Salmerón, JM Frantz, RW Beuerman, HE Kaufman, LSU Eye Center, LSU Medical Center School of Medicine, New Orleans, LA

Pilot studies in vitro and in monkeys and humans indicate that the Moist-Pak (moist chamber) tissue storage technique for Epikeratophakia Tissue Lenses is superior to the conventional freeze-dried preparation. We used immunohistochemical techniques to look for the deposition of extracellular components of the basal lamina and stromal proteoglycans, which are important indicators of normal tissue structure and function. Epikeratophakia was performed in C. aethiops monkeys using Moist-Pak Tissue Lenses; 2 months later the Tissue Lenses and host corneas were obtained by PKP The specimens were fixed in 90% alcohol for 1 hour. Cryostat sections (8 urn) were exposed to antibodies to either collagen Type IV, III, VI, proteoglycan, or fibronectin. Appropriate controls for each antibody were done. The secondary antibodies were fluorescein conjugated. Staining for collagen Type III and proteoglycan was most intense in the tissue lens stroma. A band of intense staining for collagen Type ^V was seen beneath the tissue lens and the host cornea. Collagen Type VI staining was essentially uniform in the tissue lens and host stroma. Fibronectin immunofluorescence was seen at the basal lamina of the tissue lens, but not in the host. These results suggest that the components of basal lamina are found in the tissue lens as early as 2 months after Epikeratophakia and that there is some expected remodeling of the tissue lens stroma.

Comment: This immunohistochemical study of moist pak epi illustrates the existence of a basal lamina in the tissue lenticule as early as the second postoperative month.

Dry State Epikeratophakia: A Histopathologic Study

M AbdelMegeed, B Salmerón, E Santana, RW Beuerman, SM Verity, MB McDonald, HE Kaufman. LSU Eye Center, New Orleans, LA

A method of lathing epikeratophakia tissue lenses in the dry, dehydrated state, which was developed by one of us (SMV), has been under investigation in our laboratories for the past 4 years. This method delivers a crystal clear tissue lens as the final product and offers the advantage of arrestable stages in the manufacturing process. Additionally, this less costly and more time-efficient method obviates the need to compensate for the lathe contraction that occurs during standard freeze lathe techniques. The biocompatibility of these "dry state" lenses has been tested by grafting piano powered lenses in African green and rhesus monkeys. Histologically, these tissue lenses demonstrate an absence of the changes associated with freeze injury seen in traditional methods of tissue lens preparation. Light microscopy and SEM of clinically clear tissue lenses and host corneas obtained by PKP 6 to 9 months postoperatively demonstrated that the tissue lenses were fully epithelialized and repopulated by host keratocytes. A few focal areas lacking Bowman's layer of the tissue lens were seen, mainly near and overlying the peripheral surgical scar. The stroma showed a normal appearing collagen framework in both donor and recipient tissues. The host corneas were otherwise normal. This feasibility study suggests that the dry state tissue processing method may be an improvement on current processing methods and should be studied further.

Supported in part by PHS grants EY03635, EYO2580, EYO4074, and EY02377, NEI.

Comment: Using dry state Epikeratophakia was evaluated in this poster. The authors illustrated the advantages of this technique over currently used techniques supported by LM. and TEM. However, the technique needs to be further studied for more thorough evaluation.

Postoperative Complications Following Epikeratophakia

SC Behler, K Cheng, A Biglan, D Hiles, M Pettapiece. The Eye & Ear Institute, Department of Ophthalmology, University of Pittsburgh School of Medicine, Pittsburgh, PA

Epikeratophakia was performed on a total of 88 eyes in a pediatric population. The ages of the patients ranged from 1 month to 19.4 years. Eighteen of these eyes had post operative complications. Six grafts contained interface opacities, four had epithelial defects, two epithelial melts, one graft necrosis, two infected grafts, two edematous grafts, and one traumatized graft. Ten grafts failed, five of which were successfully regrafted. !ten grafts had postoperative refractive errors greater than 3.00 diopters of spheroequivalent. Post operative complications, relative indication and contraindications in Epikeratophakia are discussed.

Comment: The poster gave a comprehensive review of the most common complications following Epikeratophakia in 88 children.

Long Term Storage of Frozen Lentlcles for Cryorefective Surgery

JJ Kownacki, KL Kratz, JW Huff, and DJ Schanzlin. Bethesda Eye Institute, Department of Ophthalmology, St. Louis University, St. Louis, MO

Freezing rates, cryoprotectants, and storage times were studied to develop a method for corneal lenticle storage, a central 7.00 mm button was removed from New Zealand white rabbits with the epithelium and endothelium removed. Control and experimental corneal buttons were incubated in either KM 26 (glycerol and DMSO in distilled water). CPTES (a TES buffered aqueous solution with 2M DMSO high in potassium and low in sodium chloride), K Sol, or TC 199 for 30 min at 4° C. Using a controlled rate freezer, we determined the optimal rate of cooling for keratocyte survival to be 27minutes. With this rate, experimental tissue was frozen to -400C, and using our keratocyte viability assay, keratocyte viabilities (expressed as percent of control) were 68.8%, 113.3%, 0.1%, and 0% for each solution respectively. KM 26 and CPTES were further studied in tissues stored at -800C. Tissue was collected as above, frozen to -8O0C, using a multicurve program, then transferred to a -800C freezer for 1, 3, or 7 days storage. Keratocyte viability for KM 26 vs CPTES after 1 day storage was 25.9% and 67.2% (p<0.001); after 3 days storage 45.3% and 64.9% (p<0.100); after 7 days storage 32.3% and 76.0% (p<0.001). These results show that the cryoprotective ability of CPTES is significantly better than that of KM 26. Use of CPTES may provide a way to store frozen corneal tissue for later use in cryorefractive surgeries.

Supported in part by NIH grant #EYO4609-07.

*Lee TJ, Wan WL, Kash RL, Kratz KL, and Schanzlin DJ: Keratocyte survival following a controlled-rate freeze. Invest Ophthalmol Vis Sci 1985; 26:1210-1215.

Comment: This is a continuation of the previous work and emphasizes the same results. Moreover, it suggests that using CPTES may provide a technique for storing frozen tissue for later use.

New Cryoprotectant for Cyrorefractive Surgery

KL Kratz, JJ Kownacki, JW Huff, and DJ Schanzlin. Bethesda Eye Institute, Department of Ophthalmology. St. Louis University, St. Louis, MO

Loss of corneal clarity after cryorefractive surgery (keratomileusis, keratophakia, and epikeratophakia) is a significant problem, with visual rehabilitation taking up to 18 months. This study examined keratocyte viability in tissue processed with either the standard cryoprotectant KM 26 (glycerol and DMSO in distilled water) or CPTES (a TES buffered, high potassium, low sodium chloride cryoprotectant with DMSO). The epithelium and endothelium were mechanically removed from corneas of New Zealand white rabbits. A 7.0 mm button was used for control and experimental samples which were placed into the same cryoprotectant for 1, 5, or 30 minutes at 4° C. Experimental buttons were frozen on a Barraquer cryolathe and thawed in 37° C MK media. We used our keratocyte viability assay* to detennine cell viability of control and frozen samples (expressed as percent viable cells). In KM 26 vs, CPTES respectively, a 1 minute incubation yielded 22.4% viability vs. 41.4% (p<0.025); a 5 minute incubation yielded 27.5% vs 62.2% (p<0,001); and a 30 minute incubation yielded 64.9% vs 76.6% (p<0.400). In our animal lamellar keratoplasty model*, autologous lenticles from NZW rabbits were incubated in cryoprotectant for 5 minutes, then frozen and thawed as above. Photo examinations were performed postoperatively at days 3, 7, and 14. The mean ultrasonic pachymetry (mm) for corneas protected with KM 26 at day 3 was 0.607 (n=4) and 0.619 (n=4) for CPTES; at 7 days 0.520 vs 0.421; at 14 days 0.408 vs 0.386. Corneal clarity was determined using the McDonald-Shadduck slit-lamp scoring system and showed a similar tendency towards faster return of corneal clarity in the CPTES group. These results suggest better keratocyte viability in CPTES protected tissue than in KM 26 protected tissue, which may minimize corneal haze after cryorefractive surgery.

Supported in part by NIH grant #EY04609-07.

*Lee TJ, Wan WL, Kash RL, Kratz KL, Schanzlin DJ: Keratocyte survival following a controlled-rate freeze. Invest Ophthalmol Vis Sci 1985; 26:1210-1215.

Comment: This poster introduces a new cryoprotectant which seems to be superior to the classic KM26. This may increase our ability to protect tissues undergoing cryolathing thus minimizing corneal haze after cryorefractive surgery.

A Comparison of the Wound Integrity Produced by Various Suture Patterns in Penetrating Keratoplasty

J Hart, SB Mahjoub, and YKAu. Department of Ophthalmology, Louisiana State University Medical Center, Shreveport, LA

A variety of suture patterns is used in wound closure of penetrating keratoplasty (PKP). We designed our study to evaluate the ability of these patterns to produce a watertight wound under increased intraocular pressure. PKP was performed on 12 cadaver eyes. Corneal thickness was reduced to physiological range using a hypertonic dextran solution. A circular button of 7.5 mm was trephined and resutured with 10-0 nylon using one of the following patterns: 1) interrupted sutures; 2) continuous (running) sutures, and 3) combined interrupted and running sutures. At completion of surgery, intraocular pressure was hydrostically adjusted and measured with a manometer as well as a pneumotonometer. Each suture pattern was tested on 4 different eyes. Wound leakage was observed at the following average intraocular pressures: a) 12 bites interrupted: 20 mm of Mercury (Hg); b) 12 bites running: 39mm Hg; c) 16 bites interrupted: 50 mm Hg; d) 16 bites running: over 100 mm Hg; e) 12 bites running combined with 6 bites interrupted: 94 mm Hg; and f) 12 bites running combined with 8 bites interrupted: over 100 mm Hg. Our results suggest that running sutures produce better wound closure in PKP than interrupted sutures using the same number of bites. Either a 16 bites running or a combined running-interrupted pattern produces superior wound closure and watertightness in penetrating keratoplasty.

Cat Keratoplasty Wound Healing and Corneal Astigmatism

KL Cohen, NK Tripoli, University of North Carolina at Chapel Hill, AD Proia, Duke University, Chapel Hill

A single published clinical study related wound pathology to astigmatism following penetrating keratoplasty (PKP). In a cat PKP model, corneal topography was measured using the Photogrammetric Index Method (PIM ). In the same cats, characteristics of wound pathology were measured and compared with a PIM Index of astigmatism. 9.50 ± 0.32 (Mean ± SEM) months after keratoplasty, the excised corneas of 18 cats who had uncomplicated surgeries and postoperative courses were fixed in 10% formalin, embedded in paraffin, and sectioned along the major astigmatic meridians. Sections from both ends of each meridian were stained (H & E, PAS) and examined by light microscopy. On a Zeiss Videoplan, wound characteristics, including the distance between donor and recipient Descemets membranes (DM), thickness of stroma and of epithelium, depth of DM incarceration, and area of corneal lamellar disruption, were measured. Stromal and epithelial thickness away from the wound were also measured. Sections were scored for the presence or absence of folds and fragments of DM. Fourteen cats had at least one wound section with less than 0.5 mm of wound between donor and recipient DM, and only two sections showed overlapping DM. DM was folded in 94% and fragmented in 83% of the wounds. Epithelium was thicker in the wound than away from the wound (p<0.001). When pathology measurements from the four wound locations of each cornea were averaged, the thicker the epithelium at the wound, the greater the astigmatism (r=0.467, p=0.05). When only flat meridional sections were considered, larger areas of lamellar disruption were associated with more astigmatism (r=0.424, p=0.05). No characteristics of the steep meriodional sections correlated with astigmatism. No cluster of wound characteristics was associated with astigmatism, and there were no significant differences between flat and steep meridional characteristics. Only thickness of the wound epithelium, which was thicker than epithelium away from the wound, predicted astigmatism.

Supported in part by the N. C. Lions Foundation for the Blind, Inc. and Research to Prevent Blindness, N. Y.

Full Thickness 16 mm Corneoscleral Grafts and HlA Typing

R Bazin, I Dubé, HM Boisiolv, R Rov, G Chamberland, J Bernier. Unité de recherche en ophtalmologie, C.H.U.L. Research Center, Laval University, Quebec, Canada.

For many severe corneoscleral pathologies, the corneal surgeon doesn't have much to offer patients in terms of reestablishing the functional integrity of the eye. Many heroic attempts to perform large diameter full-thickness corneoscleral grafts have usually been plagued by early and accelerated rejection episodes, often requiring systemic immunosuppressive therapy. We report on 7 consecutive 16 mm full thickness corneoscleral grafts all with excellent HLA compatibility but one: 3 patients had 1 HLAA, B or DR mismatched antigen for a maximum possible of 6; 3 patients had 3; and 1 patient had 5. The average age at the time of grafting was 52 years old, and the group was composed of 6 males and 1 female. The mean follow-up time was 11 months (ranging 3 to 18 months) and the preoperative diagnoses include chemical burns, severe traumatic and inflammatory scars, and fungal keratoscleritis. The distribution of the recipient bed vascularization is the following: none for 3 patients, moderate for 1 patient, and severe for 3 patients. Three patients had received prior regular sized corneal grafts (1, 2 and 5 grafts). Three patients presented endothelial rejection episodes, two of which required systemic corticosteroids and immunosuppressive therapy. Only one rejection episode finally led to an endothelial decompensation (patient with 5 mismatched antigens) and the 2 other rejection episodes have been successfully reversed, one with topical 1% predisolone acetate only. Despite major disturbances of the angle trabeculum structures by the surgical incision located 2 mm behind the limbus, none of the patients has developed glaucoma. Full thickness corneoscleral graft, previously considered a desperate last resort procedure, may develop into a reasonably good surgical alternative for the corneal surgeon in view of the good results afforded by excellent HLA matching.

Effect of Vacuum Fixation on Trephination of Donor Cornea Button

WS VanMeter, MD and S Dineen. Department of Ophthalmology, University of Kentucky, Lexington, KY

Previous reports have suggested that vacuum trephines make more symmetrical host corneal wounds than hand held trephines. To evaluate the effect of vacuum fixation of the donor rim on wound morphology, we devised a 7.5 mm plastic well with eight radial slits to permit vacuum fixation of the donor rim epithelial side for guillotine trephination. The 7.5 mm block was identical to a commonly used guillotine style block (Katena). We trephined 12 pairs of human donor rims unsuitable for transplantation. Six pairs were cut with a 7.0 mm blade and six with an 8.0 mm blade to determine the effect of blade diameter. One cornea from each pair was cut with vacuum fixation and the other was cut without vacuum fixation in standard surgical procedure with the guillotine punch. The cut buttons were immediately examined under the operating microscope subjectively for epithelial/endothelial surface area ratio (E), and then photographed and digitized to objectively determine E and wound angle deviation from the sagittal plane (-). Photographs were taken each 90° from the side on each button to measure ( - ) and symmetry of cut. Digitized photographs show that vacuum fixed buttons had more asymmetry than buttons without fixation. More asymmetry was documented with 8.0 mm buttons than with 7.0 mm buttons. Asymmetry was caused by relatively flat donor tissue conforming to the 45.00 diopter (7.5 mm) base curve well, which was steeper than all corneal tissue tested. All buttons cut with vacuum fixation had E closer to 1.0, while other 7.0 and 8.0 mm buttons without vacuum fixation had epithelial diameters (E < than 1.0). Our results suggested that vacuum fixation of the donor rim during trephination does not improve the wound configuration.

The Effect of Relaxing Incisions with Multiple Compression Suture on Post-Keratoplasty Astigmatism

JM Lustbader and MA Lemp. Center for Sight, Georgetown University Medical Center, Washington, DC

A variety of surgical procedures has been described which reduce unwanted postoperative astigmatism following penetrating keratoplasty. These include wedge resection, trapezoidal incisions, and relaxing incisions with or without compression sutures. We describe a modified technique which is performed after all keratoplasty sutures have been removed. The technique employs 3/4 depth relaxing incisions of three clock hours, 0.5mm inside the keratoplasty wound, combined with two sets of three compression sutures placed 90° from the incisions. No intraoperative keratometer is used. Selective removal of the compression sutures postoperatively, based on keratometry readings and keratoscopic appearance, allows for a graded reduction in overcorrection. The 10 patients in whom this procedure has been performed were followed for a period of 7 to 18 months; keratometry and visual acuity were charted at 3 months and 6-12 months. Reductions of 2 to 21.5 diopters of astigmatism were achieved. Mean preoperative astigmatism was 14.25 diopters. Three months postoperatively, mean astigmatism was reduced to 6.33 diopters (p<0.002). Regression of initial results between 3 and 6-12 months was seen, with mean astigmatism increasing to 7.44 diopters, as initial wound gape lessened with healing. No intraoperative or postoperative complications have occurred. This simplified technique allows for substantially greater correction of high degrees of postkeratoplasty astigmatism than previously reported.

Supported in part by a grant from RPB, Inc.

Intraocular Lens Implantation Following Penetrating Keratoplasty: Improved Unaided Visual Acuity Astigmatism and Safety in Patients With Combined Corneal Disease and Cataract

HS Geggel. Cornea Research Laboratory, Virginia Mason Clinic, Seattle, WA

Although corneal grafts remain clear following the modern triple procedure, problems with unpredictable refractive errors (anisometropia) and astigmatism occur frequently. In addition, scant information regarding unaided visual acuity has been reported after the triple procedure. Twenty-one patients with combined corneal disease and cataract had nonsimultaneous intraocular lens (IOL) placement following penetrating keratoplasty (PK). Followup was 3-36 months (mean=14) after IOL placement. Sixteen had combined PK and cataract extraction (CE) followed by IOL placement 9-14 months (mean= 11) after initial surgery. Five had PK followed by CE/IOL surgery 12-26 months (mean= 18) following initial surgery. No graft failures occurred. Sutures were completely removed in all but two patients at least one month prior to IOL surgery. Elliptical limbal wedge resections in the flat meridian at the time of IOL surgery were performed to reduce final graft astigmatism. Mean keratometric cylinder pre-IOL surgery was 4.9 diopters (D) and was reduced to 2.5D post IOL placement. Mean postop spherical equivalent manifest refraction was -0.42D (range +1.5 to -4.0). Ninety-one percent (19/21) were within ± ID and 95% (20/21) within ± 2D of emmetropia. Ninety-one percent (19/21) had 20/40 or better best corrected vision; two eyes with amblyopia had 20/60 and 20/200, respectively. Importantly, 71% (15/21) had 20/40 or better and 19% (4/21) had between 20/50 and 20/80 unaided visual acuity. The advantages of excellent unaided visual acuity, reduced astigmatism, and lack of graft failure outweigh the disadvantage of some delay in final visual rehabilitation in this series with two separate surgeries compared with previously reported triple procedure results.

Comment: The author presents 21 eyes of 16 patients with a mean age of 67 years which had IOL implantation after penetrating keratoplasty with a mean follow-up of 14.8 months after the second operation. His results showed an improvement in the visual outcome with less astigmatism, better uncorrected visual acuity, and no more risk of graft loss.

Long Temi Complications After Keratoplasty With the Combined Suture Technique

J Parker, S Feldman, J Frucht-Pery, A Parker* and S Brown. Department of Ophthalmology, University of California, San Diego, La Jolla, CA and Department of Mathematics, Palomar College*, Oceanside CA

Our study was designed to evaluate the long term effectiveness of the combined suturing technique (12 interrupted 10-0 nylon with a running Dl-O nylon) in reducing postkeratoplasty astigmatism. Twenty-five consecutive eyes underwent penetrating keratoplasty with the above technique and followup between 30 and 48 months. Preoperative diagnoses included bullous keratopathy (n=ll), keratoconus (n=6), Fuch's corneal dystrophy (n=2) and other assorted indications (n=6). In 19 eyes, 7.7 mm donors were implanted into 7.5 mm recipient beds. The six eyes with keratoconus had larger grafts (8.0 mm donors placed into 7.7 mm host beds). We evaluated the changes in keratometry and keratometric astigmatism at routine postoperative visits or at the first visit following removal of the ruptured U-O nylon suture. Eight (32%) of eyes presented with disruption of running U-O suture at 10-43 months postoperatively. While the astigmatism in the eight eyes prior to breakage (1.29 ± 1.35D) (mean ± SD) did not differ (p>.05) from the astigmatism in the rest of the eyes (1.58 ±1.10D), the postdisruption astigmatism significantly increased to 6.46 ±1.74 D (p<.001) with a range from 2.5 to 12D. The mean astigmatism for all eyes prior to suture breakage was 1.48 ± 1.17D. Astigmatism increased to 3.28 ± 2.72 D after breakage (p<.01) and mean keratometry steepened from 43.64 D to 45.71 D following breakage (p<.01). Our study indicates that breakage of the continuous U-O nylon suture results in an unpredictable increase in corneal astigmatism even years after surgery.

Non-Contact Laser Corneal Marking

H Shimada, J-M Parel, TJ Roussel, JA Lowery, K Kobayashi* and T Yokokura*. Bascom Palmer Eye Institute, University of Miami, Miami, FL and *Tbpcon Research Institute, Tbkyo, Japan

Misaligned sutures and resultant host-donor tissue disparity may significantly contribute to development of astigmatism following penetrating keratoplasty1·2 A onecontact laser corneal marking system was devised to improve accuracy of suture placement during keratoplasty and to provide topographic landmarks that are required to perform reproducible corneal mapping in animals. A 50ns pulsed hydrogen fluoride mid-infrared (2.7-3.0µp?) was coupled to a polyprismatic optical delivery system to simultaneously produce a circular array of 8 equidistant = 75 µm marks centered about the corneal apex. The diametrical location of the 8 focal marks is adjustable between 6 and 10 mm. At a fluence of = 2J/cm2, three laser pulses ablated eight identical crater-like marks in human cadaver eyes. The marks were ~ 400µm in diameter at the epithelial surface measured ~ 50u,m at Bowman's layer, but did not penetrate the latter. The non-contact laser marking technique was compared histologically to a manual technique performed mechanically with four 30ga needles mounted on a contact lens. The laser marks were more uniform in diameter and depth. Damage to adjacent tissue, often associated with mid-infrared lasers, was mainly confined to the epithelial layer which retracted away from the wound creating a larger diameter mark (400 instead of 75u-m). Thermal damage to Bowman's layer was <5um in depth; however, no changes in corneal curvature could be detected (Surgical Keratotometer SK-I, Canon). Non-contact laser corneal marking is an effective and reproducible technique which is more accurate than manual marking.

1. Olsen RJ; Ophthalmic Surg 1980; 11:838-842.

2. Pflugfelder SC, et al: Arch Ophthalmol 1988; 106:276-281.

Graft Rejection vs Graft Failure; Are There Common Causes?

ML Chipman, P Basu, A Slomovic and P Willett. Departments of Preventive Medicine & Biostatics and Ophthalmology, University of Toronto, Toronto, Ontario, Canada

The risk of graft rejection in patients receiving corneal transplants is known to be affected by host vascularization, scarring and keratitis, and possibly by a history of previous graft failure. In such cases, tissue typing and matching of donor corneas has been effective at reducing the risk of rejection. In previous work, we had shown that prior graft failure and donor cause of death were associated with graft failure. We wished to see whether the same pattern applied to rejection episodes with and without subsequent graft failure. Of 645 patients with up to three years' followup in October 1988, 89 patients experienced a rejection episode after penetrating keratoplasty, 41 of which resulted in graft failure. The earliest rejection episode occurred 21 days after surgery. A further 61 patients had failed grafts for other reasons. A total of 136 patients had either a scarred or vascularized cornea or keratitis; when the occurrence of rejection was analyzed using life table methods, these patients were at substantially increased risk of rejection (p<0.01), but previous graft failure had little influence (p>0.05). Previous graft failure and vascularization had a significant effect on ultimate success of the graft (p<0.01). Donor cause of death (trauma vs natural causes) alters the hazard of failure by a factor of 1.9, but has no effect on the hazard of rejection. These results suggest that, apart from vascularization of the cornea, the factors associated with episodes of rejection are quite different from those associated with graft failure.

Cataract Lens Implant Surgery After Keratoplasty. Safety and Refraction Predictability

PS Binder. Ophthalmology Research Lab, Sharp Cabralo Hospital, San Diego, CA

When confronted with an eye with a combined leukoma and cataract, some surgeons recommend performing the transplant first to obtain stable keratometry readings to improve post-op refractive errors following subsequent cataract and intraocular lens (IOL) surgery. Thirty four consecutive eyes that had previous transplants performed by the author underwent subsequent extracapsular cataract extractions with IOL implantation, (31 posterior chamber IOLs) or secondary lens implantation (2 AC, 1 iris) an average of 30 months after surgery (range 3-128). The mean follow-up after IOL surgery was 21.6 months (range 6-72). Eight grafts (23%) failed 2 weeks to 12 months after the secondary surgery due to recurrent host disease (2 HSV) or endothelial failure (6 eyes). Twenty three eyes (66%) achieved 20/40 or better best corrected acuity. None required contact lenses. Twenty five of 32 (78%) had post-op refractions within 2D of emmetropia. Although surgery was performed to reduce pre-existing keratoplasty astigmatism (3.35D ± -2.2D), postop astigmatism was not reduced (3.99D ± -2.91SD). The time from the original corneal transplant to final spectacle prescription after lens surgery exceeded 30 months. In contrast, of 117 consecutive triple procedures with posterior chamber IOLs performed concurrent to the above series with a mean follow-up of 30 months (range 6-97), 77.8% were 20/40 or better an average of 8 months after surgery, 68% were within 2D of emmetropia, 95% are clear, three require contact lenses, and the mean astigmatism is 3.5D ± 2.2D. Based on this series, there is no advantage to performing lens surgery after keratoplasty under the guise of improving refractive predictability.

Comment: The author presented 33 eyes that had IOL insertion after penetrating keratoplasty, of which 22 had cataract extraction, 10 were contact lens intolerant, and one had an IOL exchange for a power error. This series was compared to 117 eyes which had triple procedure. Theauthor concluded that performing lens extraction with IOL insertion after penetrating keratoplasty may slightly improve the refractive outcome, but there is a greater risk of graft failure, more chance of reactivation of herpes simplex virus, and no reduction in postoperative astigmatism- Therefore, he recommended the triple procedure.

Factors Affecting Success of Penetrating Keratoplasties

L Hyman, C Yang, R Grimson, J Wittpenn. SUNY Stony Brook, Stony Brook, NY

The increasing demand for penetrating keratoplasties (PK) necessitates careful evaluation of factors predictive of graft clarity. Data were collected on 819 PK patients who received tissue from affiliates of Tissue Banks International Inc., and underwent surgery between July 1984 and January 1985 at one of several institutions. Followup information on graft clarity within one year was obtained from the operating surgeon on 89% (733/819) of these patients. Data were analyzed by chi- square and t-tests and by multivariate analysis. Cumulative graft clarity rates at one year after PK were lowest for failed grafts (60%) and highest for keratoconus (88%). Patients with corneal scar, corneal edema or corneal dystrophy had graft clarity rates of 76%, 81% and 85% respectively. Multiple factors were evaluated with respect to graft clarity. Those that demonstrated no statistically significant effect on graft clarity include age of donor tissue, age matching of donor and recipient, cataract between donor's death and tissue preservation, quality of donor tissue, age matching of donor and recipient, cataract removal or vitrectomy at the time of transplant, use of an IOL, suture size and type, and surgical technique. Factors demonstrating an independent significant effect on graft clarity were previous graft failure (p<.001), vascularization (p<.001), inflammation (p=.001), surgery done for emergency purposes (p<.001), surgery done for restoration (p=.007), glaucoma (p=.03), complications during the transplant (p=.003), and race (p=.04). Multivariate analysis suggests that previous graft failure, vascularization, and complications at surgery were most strongly associated with lack of graft clarity. Knowledge of both the significant and on-significant factors may influence surgical and postoperative management.

This work was supported by Tissue Banks International Inc.

Mechanical Properties of Rabbit Cornea

E Morales, A Clarke, R Spedale, Jr., R Beuerman, D Rice, R Anderson, P Gebhardt. LSU Eye Center, New Orleans, LA

Good vision requires maintenance of the structural integrity of the stroma, a composite of collagen fibrils embedded in a viscoelastic matrix of polyanionic macromolecules. Tfensile and stress-relaxation measurements on the stroma permit assessment of the mechanical properties of the collagen and matrix. Corneas from white New Zealand rabbits (5-6 lb) were obtained from an abbatoir and stored in a refrigerated, moist chamber for 36 hours (fresh) or in a solution of K-SoI for 5 days (stored). Corneal strips, 5mm wide, were held by clamps in a tensile testing machine and stretched at a constant rate of 6.35mm/minutes until failure. Stored corneas showed a reduction in tensile strength. Young's module in fresh cornea was 5.3 MPa (106 Newton/m2) vs 4.2 MPa in stored cornea (p<0.05). Stress relaxation tests stretched the tissue at 50mm/minutes to an elongation of 32%. Tissues were held in the elongated position for 120 seconds, relaxed at 0%, elongation for 120 seconds, and then stretched as before. The stress relaxation time constant was 1-2 seconds in the first stretch. On the second stretch, the peak was 30% to 40% of the peak on the first stretch; the relaxation time constant was 12-15 seconds. These results indicate that corneal storage weakens the structural properties of the stroma. Breakdown of the polyanionic matrix may be involved in this effect and in the increased time constant. This work was supported in part by NIH grant EY04074 and EY02377.

Heterologous Transplantation vs Enhancement of Human Corneal Endothelium

MS Insler, JG Lopez. LSU Eye Center, New Orleans, LA

The ability to successfully transplant human corneal endothelial cells (HCEC) would offer a significant advance in the treatment of many corneal diseases. To investigate the feasibility of this, we cultured neonatal HCEC and seeded the cells onto adult human corneal buttons which were either denuded of their native endothelium or possessed of an intact endothelial monolayer. The buttons were cultured for 48 hours and then transplanted into green monkeys using routine PKP techniques. Pachymetry revealed progressive stromal thinning in both groups, however, the rate of graft failure in the seeded buttons remained lower (35%) than that of the enhanced buttons (60%). By 5 months the mean corneal thickness for the seeded group was 0.52mm and 0.70mm for the enhanced group.

Control eyes in which the native endothelium was removed showed advanced corneal edema and vascularization; the average corneal thickness was in excess of 1mm. Histological evaluation of the failed enhanced buttons revealed poor incorporation of the cultured endothelium into the monolayer and retrocorneal membrane formation, suggesting HCEC metaplasia. Failure in the seeded buttons was attributed to xenogeneic graft rejection. These results reveal that transplanted HCEC can function normally and suggest the possibility of endothelial cell replacement for therapeutic purposes.

This work was supported in part by NIH Grant EY07608-02.

Quantitation of Rabbit Corneal Epithelial Migration on Polymeric Substrates in Vitro

*DKPettit, *tASHorbett, *fAS Hoffman, and **KYChan. *Center for Bioengineering, fDepartment of Chemical Engineering and **Department of Ophthalmology, University of Washington, Seattle, WA

The successful development of a totally synthetic corneal graft depends, in part, on the ability of corneal epithelial cells to migrate onto a synthetic surface and form a continuous multilayer of functional cells. Tb study the effects of polymer surface properties on corneal epithelial cell migration, a quantitative cell migration assay was developed. Circular expiants from rabbit corneas were placed on the following polymeric substrates: poly(hydroxyethyl methacrylate/ethyl methacrylate) copolymers, poIy(styrene/phydroxystyrene) copolymers, tissue culture treated polystyrene, polyethylene, polydimethylsiloxane, and polytetrafluorethylene. These materials were characterized by Electron Spectroscopy for Chemicai Analysis (ESCA) for surface chemical composition and by captive air bubble contact angle for surface wettability. Following 4 days of epithelial cell migration onto the test substrates, the cells were fixed and stained, and the cell outgrowth areas were measured by digitization. In order to reduce the variation in outgrowth between corneas from different animals, a control surface (tissue culture treated polystyrene) was tested with each cornea, and a ratio was made between the area of outgrowth on the test surface and the area of outgrowth on the control surface. A relationship was found between epithelial cell migration and the wettability of the polymer substrates. The greatest epithelial cell migration was found on substrates with intermediate wettability. Although the polymers tested in these experiments would not be useful for corneal grafting due to their inadequate permeability characteristics, these results suggest that epithelial cell migration may be optimized by synthesizing or modifying existing polymers with high nutrient permeability to generate surfaces with intermediate wettability.

Supported by Allergan Medical Optics, Irvine, CA, and in part by NHLBI grants HL19419 and HL33229-04.

Promotion of Graft Survival by Photothrombosis of Corneal Neovascularization

G Corrent, T Roussel, SCG Tseng, BD Watson. Departments of Ophthalmology and Neurology, University of Miami School of Medicine, Miami, FL

Corneal neovascularization is a condition which may not only compromise visual function, but also reduces the success of penetrating keratoplasty for visual rehabilitation. Photothrombosis using intravenous rose bengal and argon laser has shown promise for occluding corneal neovascularization (Huang et al, Arch Ophthalmol 1988; 106:680). It is therefore conceivable that photothrombosis of corneal vessels can improve the outcome of corneal transplantation in vascularized areas. Using intracorneal 7-0 silk sutures as the stimuli, corneal neovascularization was induced in one eye of 19 NZW rabbits. Eleven eyes received photothrombosis as previously described. Corneal vascularization was successfully occluded with subsequent regression, as verified by corneal angiography. Among these, three were assigned for observation and eight for subsequent penetrating keratoplasty with donor corneas from outbred rabbits. In 6 of 8 eyes receiving grafts after thrombosis, the graft remained clear during 8-18 weeks of follow-up, while graft rejection occurred in 7 of 8 control eyes without photothrombosis (12.5% survival). These results indicate that photothrombosis of corneal vessels prior to corneal transplantation can promote graft survival (p<0.05) in this experimental model and may have clinical significance.

Supported by EY06819, NS23244, and EY02180.

Effect of Donor-Recipient Age Matching on Endothelial Cell Loss After Penetrating Keratoplasty

AE Schwartz, DC Musch, A Sugar, RF Meyer. Department of Ophthalmology, WK. Kellogg Eye Center, The University of Michigan, Ann Arbor, MI

Age matching between the corneal donor and recipient in penetrating keratoplasty (PK) is used by some surgeons, with the rationale that it would be unwise to place an "old" donor cornea in a young recipient. In order to evaluate this possibility, we assessed change in endothelial cell density (ECD) within patients undergoing PK for keratoconus (KC, n=201) and Fuchs' endothelial dystrophy (FD, n=143). All pre- and postoperative information was obtained from the computerized files of the Michigan Corneal Transplantation Patient Registry. Change in ECD was assessed among three age-match strata: donor age ten or more years greater than recipient age (D>R); donor age within ten years of recipient age (D=R); and donor age ten or more years less than recipient age (D<R). Within KC patients, there were no significant differences among the three age-match groups' ECD decrease for time-specific analyses through three years after PK (e.g., at two years post PK, =D decrease was: D>R, 26.2%; D = R, 27.9%; D<R, 35.5%). Within FD patients, however, a significant effect was observed. Initiating at one year after PK, and continuing through three years post PK, percent ECD decrease within the D<R group was less than the D=R group (e.g., at two years post PK, = D decrease in the D= R group, 46.2%; in the D-R group, 22.6%). These results, if substantiated by further studies, would indicate that it is beneficial to use younger donor tissue in an older recipient. Younger recipients, however, show no adverse effect on ECD upon receiving relatively older donor tissue.

Procine Collagen Corneal Shield Treatment of Persistent Epithelial Defects Following Penetrating Keratoplasty

LR Groden, W White, S Updegraff. Department of Ophthalmology, University of South Florida, Tampa, FL

Treatment of persistent epithelial defects (PED) following penetrating keratoplasty (PK) can be" difficult. The use of a 24-hour porcine collagen corneal shield, Bausch & Lomb, to promote epithelization of these cases was compared to the use of the hydrophilic bandage soft contact lens (BCL) Bausch & Lomb plano 04. Twenty-three consecutive patients treated for PED following PK were reviewed. Sixteen of 22, 73%, treated with BCL healed completely. Zero of seven (7), 0%, patients with PED treated with collagen shield therapy healed. Six (6) of these seven (7) patients were subsequently treated with BCL; five (5), 83%, healed with BCL therapy. These data suggest that the 24-hour collagen corneal shield is not useful in treating PED following PK and that BCL is significantly more effective, p<0.01, in these cases.

Human Corneal Endothelial Transplantation in the Rat Penetrating Keratoplasty Model

EJ Holland, H Tchah, D Skelnik, C Chan, M Ni and RL Lindstrom, University of Minnesota, Minneapolis, MN and Laboratory of Immunology, National Eye Institute, Bethesda, MD

Lewis rat corneas denuded of endothelium were seeded with cultured human endothelium and incubated for five days in serum supplemented CSM at 35.5oC. These seeded corneas were used as donors for penetrating keratoplasties in Lewis rat recipient thus resulting in an endothelial xenograft with a syngeneic graft of stromal and epithelium. Of the rats transplanted with seeded corneas, 12 were treated with systemic cyclosporine A (CsA) and 9 received no immunosuppression. Ten Lewis corneas with the endothelium denuded and not replaced were used as donors for controls. Clinical evaluations on each graft were conducted for three weeks then immunohistochemical studies were completed. All of the non-immunosuppressed rats and 8 of 12 CsA treated rats had graft rejection by the third week. This was characterized by edema, graft haze and neovascularization. Four of twelve CsA treated rats did not reject. These grafts remained thin and clear with mild neovascularization around the sutures. Immunohistochemical studies of the transplants which rejected revealed diffuse graft infiltration with T suppressor/ cytotoxic cells., T helper/inducer cells and macrophages. There was enhanced expression of class I (QX 18) and class II (OX 6, OX 17) antigens in the epithelium and keratocytes. The few attenuated endothelial cells present were rat as determined by the presence of rat class I antigen (OX 18). Stains for human class I (PHM4) and human endothelium (PHM5) were negative. CsA treated rats which did not reject had a normal appearing monolayer of endothelium with few inflammatory cells surrounding the sutures. Approximately half of the endothelial cells were human (PHM4+ and PHM5+) and the remainder were regenerated rat endothelium (OX 18+ ). This study demonstrates that a xenograft of endothelium on syngeneic stroma and epithelium can elicit a rejection reaction. If the rejection is prevented with CsA a functional endothelium can survive but is partially replaced by regenerated rat endothelium in this model.

XXIXth Nordic Ophthalmological Society

Refractive Surgery In Scandinavia

June 18-21, 1989

Reykjavik, Iceland

Reported by UIf Stenevi, Lund, Sweden

Every other year the Nordic Ophthalmological Societies hold a joint scientific meeting and June 18-21, 1989, the XXDCth Nordic Ophthalmological Society met in Reykjavik, in Iceland. Dr Ingimundur Gislason and his colleagues from Iceland (there are less than two dozen ophthalmologists in all of Iceland) hosted close to five hundred active participants from Denmark, Norway, Finland and Sweden. The first day of the meeting was devoted to instructional courses and the following three days had main single sessions in the morning and multiple sessions for free papers in the afternoons. All together 119 scientific papers were presented covering almost all fields of ophthalmology.

For the first time ever refractive surgery was on the program. In fact half a day was devoted to refractive surgery. The first part of the morning Professor Richard Lindstrom from Minneapolis, Minnesota introduced refractive surgery with his plenary lecture "Radial and Astigmatic Keratotomy." After this very elegant and much appreciated introduction the stage was set for a symposium called "Refractive Surgery in the Nordic Countries Today." In seven short presentations most of the refractive surgery being performed in the different Nordic countries was summarized.

The session was concluded with a round-table discussion with the previous speakers and the topic was Refractive Surgery in the Nordic Countries Tomorrow. As moderator of the symposium and the round-table discussion I would like to briefly summarize the two here.

Refractive surgery has been and still is a very controversial subject in the Nordic countries. Penetrating keratoplasty, however, is a common and non-controversial surgical procedure. The main indication for penetrating keratoplasty is, in contrast to the United States, not Pseudophakie corneal edema but rather keratoconus, corneal dystrophies and corneal scars.

Radial keratotomy is performed on a small scale in all countries. Any general agreement on the indications for RK was hard to find even though only one or two clinics in each country perform the procedure. The overwhelming majority of ophthalmic surgeons do not perform radial keratotomy. It remains to be seen if the results presented will change this attitude. Epikeratoplasty of different techniques seems to be less controversial. The largest material by far was presented outside this symposium by R.J. TJusitalo and coworkers from Helsinki, who presented a two year follow-up of epikeratophakia for keratoconus.

Surgery for correction of astigmatism is still at its infancy but seemed also to be a less controversial subject. The material from Lund, presented by Ingrid Floren, seemed to correlate well with the results earlier presented by Professor Lindstrom in his extended presentation on Astigmatic Keratotomy. In their closing remarks practically all the participants looked to the future with some confidence and expressed their hopes that the excimer laser might add more predictability and reproducibility to refractive surgery.

Refractive surgery has had a slow start in the Nordic countries but it is always difficult to predict the future. We should remember that 10 years ago practically no intraocular lenses were used in these countries. Today implant frequencies of intraocular lenses is higher in the Scandinavian countries than anywhere else in Europe and is quite comparable to the implant frequencies reported from Canada and Australia.

Apart from the scientific sessions, Iceland had a lot to offer everyone. The organizing committee presented a unique social program of outstanding quality. The opening ceremony in the church of Hallgrimskirkja was honored by the President of Iceland, Mrs Vigdis Finnbogadottir. Excursions to natural hot baths were mixed with an opera performance and sightseeing around the city of Reykjavik. Iceland, located at the level of the arctic circle, offers a unique climate and a rugged and spectacular landscape. In June, the midnight sun is constantly illuminating this island with its rapidly changing weather, where an umbrella is always pertinent. The few brave participants in the Midsummer-night Golf Tournament will remember for ever the midnight sun, the raving sea, the drizzling rain and the four hours struggling with the seagulls, the golf balls and the elements of nature. To an independent observer, this behavior on a seaside golf-course at four o'clock in the morning might be considered controversial in the same manner as refractive surgery; however, in Iceland in June 1989 it was not.

Abstracts from the symposium REFRACTIVE SURGERY IN THE NORDIC COUNTRIES TODAY presented in Reykjavik June 20th, 1989

Radial Keratotomy Since 1983

Niels Ehlers and Jörgen Andersen, Aarkus, Denmark

We performed our first case of radial keratotomy (RK) in 1983. The number of operations was small until 1986 when the populations interest had increased and a systematic examination program was set up. We present here the case history with onset and development of myopia, preoperative measurement of cycloplegia by subjective and automated refraction, corneal curvature, axial length, depth of anterior chamber, thickness of central cornea, intraocular pressure, corneal sensibility, and a photokeratoscopic examination of the peripheral and central corneal surface.

Surgery has been performed with a diamond knife, the number of incisions have been between 4 and 16, depth of incision 80% to 100% of optical thickness, optical zone 3 to 4 mm. Follow-up examinations have been performed regularly at 1 week, 1 month and 6 months. The number of patients is around 150 (300 eyes). Recently, pre- and postoperative examination of contrast sensitivity has been included in the study. The standard method comprises today: preoperative keratometry and pachometry, operation under the Zeiss surgical keratometer, depth of incision 100% of central corneal thickness, centrifugal incisions with deepening of the incisions centrally by cutting towards the center, number of incisions varied according to peri -operative change in curvature, which correlates with one month results. Some of the data will be presented and form the basis for the discussion on indications.

Refractive Surgery In Finland

Ilkka Raivio, Helsinki, Finland

The two more important methods for refractive surgery used in Finland today are epikeratophakia and RK. National Board of Health has assigned some rare diseases to be treated or new methods to be used in certain hospitals only. Epikeratophakia is done in three centers. Main indication in children is cataract. Best results have been obtained in traumatic cataracts. It also has been used in adult aphakia and keratoconus.

RK has been regarded more or less a cosmetic procedure. Long waiting lists for cataract operations in the general hospitals have required the use of available resources mainly to the treatment of actual diseases. RK has been started by private practitioners only. So far two ophthalmologists in Finland practice RK in any larger scale. Since August 1988 about 140 RKs have been performed.

The Soviet RK is widely advertised in Finland by TV and travel agencies. Thus the patients in Finland have three choices for RK: privately in Finland, in Moscow or in the USA. The price range varies from 6.000,- FIM (in Finland) to 15.000,- -(in USSR). In the Russian price the travel and accommodation is included. However, in Finland the price includes follow-up and additional treatment. In the USSR there is no follow-up. Possible complications have to be treated at home. The standards regarding patients' rights are different.

The 140 RK performed in Finland seem to correspond with the PERK results. Most of the cases have been selected in the 2 to 7 D range.

Epikeratophakia/Epikeratoplasty for Keratoconus

Gunnar Hovding and Torstein Bertelsen, Bergen, Norway

Epikeratophakia has been done in 15 keratoconus patients unable to wear contact lenses. The epithelium was removed from both the donor and the recipient cornea. Lamellar grafts with a diameter of 8.5 mm and a thickness of 0.15 to 0.30 mm were handcut from fresh donor eyes. In the first 3 patients the periphery of the graft was sewn into a circular keratectomy with a diameter of 7.5 mm. In the remaining 12 patients the edge of the graft was secured into an interlamellar cleft in the recipient cornea with an inner diameter of 7.1 mm and an outer diameter of about 10 mm. Compared with a penetrating keratoplasty the epikeratophakia has several advantages. It is an extra-bulbar procedure, and the risk of graft reactions appears to be very small. When a fresh, not frozen donor cornea is used, the graft is clear from the first postoperative day, and reepithelialization takes place within the first week after surgery. The procedure gives a highly satisfactory flattening of the central cornea, and the border between the recipient Bowman's membrane and the graft becomes virtually invisible. The main disadvantages of the epikeratophakia procedure are that wrinkles and opacities in the recipient cornea may tend to produce a glare, and that a relatively time-consuming postoperative care with selective suture removal is often necessary to achieve as little postoperative astigmatism as possible. Details regarding pre- and postoperative visual acuity, surgical technique, postoperative care and complications are presented.

Experiences With Keratotomy

Jens G. Hetland, Oslo, Norway

The technique of keratotomy for astigmatism and myopia is of great benefit for patients not able to wear contact lenses, feeling disabled by spectacles in their professional life or physical activities.

The technique should not be postponed until better or more predictable methods have been developed. The new methods not only need to be better, but they would also need to be included within the general health service of the country. Surgery with excimer laser is therefore not a realistic alternative in Norway in the foreseeable future.

There is little correlation between readings with the Javal-Schiotz keratometer and the refraction in the optical zone after keratotomy. The most perplexing images might be seen, but nevertheless the patient has an uncorrected V.A. of 20/20 without any astigmatic distortion.

The author has worked out a theoretical model of the main supporting structures of the corneal dome. This model might be of help when performing keratotomy and when explaining the surgical procedures for the patient.

According to the model not only 4, 6 or 8 radial incisions may be made, but also 3, 5 or 7 - thus giving the surgeon a broader choice of alternatives. More research is needed, however, before an unequal number of radial incisions can be recommended.

At least one of the Norwegian Universities should have the possibilities and resources to enter into the field of research within refractive surgery.

Many more patients than usually thought of have disabling handicaps due to refractive errors.

Radial Keratotomy - Results and Complications

UIf Stenevi and Ingrid Floren, Department of Ophthalmology, Lund, Sweden

The first 35 eyes that underwent radial keratotomy (RK) by a beginning RK-surgeon were evaluated. The indications of surgery were: a) stable myopia <8 D b) >20 years of age, c) Contact lens failures, d) Glasses unacceptable, e) Occupational needs, f) Fully informed patient.

The depth of the diamond blade was set under a calibrating microscope. Four or, if necessary, eight radial cuts were performed under retrobulbar anesthesia. Follow-up time ranged from three months to two and a half years. Thirty one eyes saw 0.5 or better (14 saw 1.0 ) uncorrected postoperatively. One eye was overcorrected and 3 undercorrected. The three undercorrected eyes (visual acuity <0.5) were reoperated and one of these three eyes required a third operation due to induced astigmatism.

The well-known epiphora, light sensitivity, glare and fluctuation of vision were noted postoperatively. In no case has this become permanent. A surprising finding was that the uncorrected visual acuity was often better than the reduction in the keratometric readings would indicate. The importance of correct patient selection is stressed.

Relaxing Incisions After Penetrating Keratoplasty

Ingrid Floren, Ulf Stenevi, Department of Ophthalmology Lund, Sweden

Due to high postoperative astigmatism following penetrating keratoplasty ten eyes were operated on with relaxing incisions over a period of 2 and a half years.

Three of the eyes had been transplanted more than 20 years before, two eyes 5 to 10 years and five eyes 1 to 3 years before. The reason for keratoplasty was keratoconus in nine eyes and endothelial dystrophy in one eye.

Astigmatism post keratoplasty ranged from 4 to 18 D. Relaxing incisions were made opposite to each other 90° around the axis of the steepest meridian. A metal blade was used for dissection of the host graft interface as deep as to Descemet's membrane.

Microperforations occurred in three eyes. Another eye was sutured because of leakage despite a bandage contact lens.

The mean reduction of astigmatism was 5.3 D with a range from 2.5 to 8.0 D.

The axis of the steepest meridian was essentially unchanged in eight eyes but shifted 110° in one eye and 150° in another eye.

Summary of the Third Congress of the European Refractive Surgery Society

June 2-3, 1989

Antwerp, Belgium

Reported by Perry S. Binder, MD, FACS, La Jolla, Calif

The third meeting of ERSS took place on June 2 and 3, 1989 in Antwerp, Belgium at the Switel Hotel which was located 100 yards from the Antwerp Zoo and two blocks from the central train station. Approximately 250 registrants attended the two-day meeting that covered all of the current approaches to refractive surgery. Each plenary session was moderated by two experts in refractive surgery. Although many excellent papers were presented, space limitations only allow comments on a few of them. The entire program is Usted below.

The papers on keratomileusis confirmed the capability of this technique to correct large amounts of myopia. J.L. Couderc compared the results of 85 myopic keratomileusis procedures performed using current cryolathe techniques to 35 cases of myopic epikeratoplasty. It was his opinion that the keratomileusis procedure produced more rapid vision recovery with fewer complications. The highlight of the session was the first Barraquer lecture sponsored by the European Refractive Surgery Society which was given by Dr Jörg Krumeich of Bochum, West Germany. In his excellent review of the development of the freeze and nonfreeze keratomileusis procedures, Dr Krumeich stressed the importance of leaving the host Bowman's membrane intact in order to achieve the best possible refractive results. He has found that using a thinner anterior cap of 0.21 mm for the refractive cut produces better results with the BKS instrument. He presented the use of a new suction fixation ring that can be used for in-situ keratomileusis, which allows different diameter discs and stroma to be resected using the same ring without removing it from the eye.

The second session on high myopia was highlighted by three presentations that use myopic anterior chamber lens implants in phakic eyes. Most interesting was a paper by Montard and coworkers who presented a comparison of 27 consecutive cases of non-freeze myopic keratomileusis and 28 phakic myopic anterior chamber lens implants. He concluded that the predictability of postoperative spherical equivalent refraction was better in the intraocular lens implant group.

The entire Friday afternoon session and most of the morning session on the second day was devoted to radial keratotomy.

Dr Lopes-Cardoso was unable to find a correlation between intraoperative and postoperative keratometry following radial keratotomy. One of the coordinators of the meeting, Dr Luc Haverbeke, presented the results of 840 consecutive radial keratotomy cases performed in 1988 using centripetal incisions. It was his opinion that if a significant undercorrection occurred with a fourincision procedure, the addition of four incisions at the same optical zone diameter would only improve the correction by 10%. An undercorrection following an 8incision procedure would have only a 5% improvement with an additional four incisions at the same optical zones. If an undercorrection occurred after four or eight incisions, using an optical zone 0.5 mm smaller in diameter for additional incisions achieved an average improvement of 0.75 D. A 1-mm smaller diameter optical zone for additional incisions improved the correction to 1.25 D. However, he felt that peripheral redeepening was the most effective approach to undercorrections, improving the refraction between 1 and 1.5 D.

Dr Krumeich presented a 2-year follow up of 89 eyes that had undergone radial keratotomy with the RK Bridge (which he designed). Sixty-one percent of the eyes achieved refractive errors within 1 D of emmetropia and 100% of the eyes achieved refractive errors within 2 D of emmetropia. Dr Umberto Merlin studied the clinical results of radial keratotomy, concluding that the sharpness of the diamond blade determines the ultimate refractive results. A dull knife creates irregular incisions which create wider scars.

Dr George O. Waring IH presented his impressions of "What We Have Learned From the PERK Study." These lessons included: centering refractive surgical procedures over the pupil; using 15Ox magnification to calibrate blade extension; using centripetal incisions for more uniform incision depth; a refractive goal not of emmetropia, but of -0.5 to -1 D; symmetrical outcome with 75% of the eyes achieving refractive errors within 1 D of each other and 98% of the eyes achieving refractive errors within 3 D of each other; 66% of the eyes not requiring any form of optical correction; corneal topography revealing "multifocal" optics following radial keratotomy; reoperations being less predictable than the primary procedure; age as the only patient variable that measurably affects the outcome; and a continued effect of the operation in 13% to 26% of the eyes depending upon the studies cited.

Dr Merlin presented evidence that the rapidity of an incision can decrease incision depth by approximately 10%. Dr Ventor from South Africa reported the results of 200 cases of four- and eight-incision radial keratotomy procedures performed with centripetal incisions. He performed peripheral deepening at the 5- and 7-mm optical zones when he added four to 16 incisions. He was able to improve the refractive results from 0.75 to 2.14 D with a 55% perforation rate.

The last morning session on Saturday was devoted to intracorneal implants. Dr Gabriel van Rij and Dr Perry Binder presented the results of aphakic and myopic intracorneal hydrogel implants in animals and in limited clinical trials, documenting good biocompatibility. Gabriel van Rij emphasized that the aphakic intracorneal lens should be placed at about 50% depth for best predictability of refractive result.

The laser session chaired by ERSS president, Dr Daniele Aron Rosa, discussed the current clinical results. Work at the Rothschild Institute by Dr Ganem suggested that newer laser technology could create radial excisions with more precision than the diamond knife. Clinical results presented by Dr Aron Rosa suggested the late development of anterior stromal haze underneath the area of excimer ablation.

An interesting paper presented the preliminary clinical results using the YAG Laser to create intrastromal corneal lesions. Superficial and deep lesions damaged both Bowman's and Descemet's membranes. The authors felt that mid stromal lesions created 1.5 D of keratometry change.

THURSDAY JUNE 1. 1989

17.00-19 00 Welcome & Regislralion

FRIDAY JUNE 2, 1989 MORNING

8.30 Registration & Stands

Keratomileusis session : Moderator : Professor J. Krumeich & J.L Couderc

9.00 Arena-Archil« Keratomileusis in situ- global talk.

9.10 Couderc Kératoplastie lamellaire s.ins congélation : 3 ans d'expérience.

9.20 Laroche Non-Freeze Keratomileusis.

930 Buratto SKS 7000 Non-treeze KM; lirst results.

9.40 Martinski Puissance optique de la kératophakie : Étude théronque.

9.50 Navarro Keratomileusis m situ. Personal experience 9.50

10 00 Krumeich BARRAQUER LECTURE : Non-lreeze Keratomileusis A ERSS AWARD TO DR. KRUMEICH

10.10 Panel discussion wilh ail speakers

10.30 Cotlee-break S Slands

High myopia session : Moderator Franco Venelia & François Pithon

11.00 BaiVoff Implants negatils de ctiamb'e antérieure : 100 cas dans 8 centres.

11.10 Worst Implant négatil intraoculaire pour myopie torte.

11.20 Fuña mon approche des grosses myopies.

11.30 Gould How to extend the range in PK.

11.40 Mawa* Powercalculation in high myopia.

11.50 Meur Extraction du cristallin clair dans la myopie Ione

12.00 Montard Comparaison de KM myopque versus l'implant negati!

12.10 Animaled discussion between and with the speakers

12.30 Work lunch

FRIDAY JUNE 2, 1989 AFTERNOON

Radial Keratotomy sesalon : Moderator : Luc Haverbeke A Fabio Doaal

14.00 Banamou Le pansement en collagene : réel progrès ?

14.10 Prtjot La jurisprudence en chirurgie retractive.

14.20 Pithon Informatique, instruments et prix en kératotomie radiane.

14.30 M*ur KR du troisième age

14.40 Mattys Faut-il taire les 4 incisions en croix latine ou en croix maltaise ?

14.50 litre Comment les 'experts' opèrent des astigmatismos simples ?

15.00 Leroux Résultats d'opérations pour astigmatismes myopiques.

15.10 L*vy Expériences à propos de la cicatrisation cornéenne.

15.20 Le bu I taon La primauté des nomogrammes pour K.R.

15.30 Dvrviiiiar La thermokératoplastie pour hypermétropie : technique Russe.

15.40 Doni KR et endothelium corneen.

15.50 Table ronde avec les orateurs.

16.00 Corlee break & Slands

Varia : Moderator : Lucio Buratto & Chad Rostron

16.30 Marmar The corneal collagen shield.

16.40 Mawa Acuité visuelle et ëblouissement.

16.50 Pacalon Conception d'un kératomètre chirurgical.

17.00 Joyeux La lutte contre la presbytie 1 7 10 Panel discussion with ine speakers and the ERSS committee.

18.00 RECEPTION AT THE TOWNHALL.

20.00 GALA DINNER af 'St Jacob m Gahcie' m the old city, near the townhall.

SATURDAY JUNE 3. 1989 MORNING

Radial Keratotomy session : Moderator : Perry Binder A Umberto Merlin

9.00 Schapira My pachymetnc measurements.

9.10 Lopee-Cardoso Value ot the peroperative keratometry.

9.20 Binder Incision direction in RK

9.30 Haverbeke Touching up an undercorrected R

9.40 Krumeich Electronic RK knite with depth control by a tootpedal; fixation with a succion bridge

9.50 Merlin A rare complication in RK * Epithelialisation ot the wound

10 00 Waring Ma/or lessons trom the PERK study

10 10 Manner Radial thermal hyperopic keratoplasty : personal experience

10 20 Grady Hexagonal keratotomy tor hyperopia.

10 30 Kern The Kern hyperopic keratotomy

10 40 Gosheh The Calitornia experience ot marketing RK

10 50 Venter Analysis ot 2000 consecutive RKs

11 00 Discussion and question answering by the speakers

11 30 Slands & Corlee

Inlay-session : Moderator : Dan Epstein & Michel Montard

12 00 Van Rij Intracorneal hydrogel inserts in primates and in humans.

12.10 Colin Implants cornéens mtrastomaux

12 20 Laroche Hyctrogets en chirurgie cornéenne.

12.30 Work lunch

SATURDAY JUNE 3. 1989 AFTERNOON

Laser session : Moderator Danielle Aron Rosa & René Trau

14.00 Epstein Laser today - Laser tomorrow

14.10 Höh Retractive surger/ with the yag laser.

14 20 Aron-Rosa-Ramirez-Timsit Update in Excimer laser techniques

14.30 Dausch Excimer laser in RK

14.40 Ganem Ettet secondaire des kêratolomies a l'excimer

14.50 Round table with the speakers 14 50

15.15 Coffee pauze

Room Spa-Mallorca

IOL session : Moderator : Ren* Trau & Kelman Wisnia

15.40 Zeyen Bitocal lOL's.

15.50 Linnik IOL with natural spectral caracteristics.

16.00 Van Oye Bitocal lOL's

16.10 Aflalo Retming IOL power calculation.

Epi-session : Moderator : George Waring & Georges Baikoff

16.20 Am* Etude hislologique de l'épi plane.

16.30 Colin Epi sans congélation 16 30

16.40 Delbosc Organ culture preservation ot corneal lenticules lor epigratting 1640

16.50 Ganem Epi-BKS chez des entants Technique; résultats; complications.

17.00 Leroux Résultats de I! épigrettes lyophilisées chez de jeunes aphaques unilat

17.10 San Giuolo Sur 282 epikeratoplasties : études paraleles.

17.20 Rostron Epigratts glued with autologous cryoprecìpitate

17.30 Rise Astigmatisme et Epikeratophakie : 40 cas.

17.40 Lipshitz Case report : RK. after epi failure and removal

17.50 Refractive and Corneal Surgery Journal: George O. Waring

SUNDAY JUNE 4, 1989 AT 10 A M

4 counes

1 HK. course Dr Haverbeke Room St Moritz

2. Astigmatism course Dr Merlin Room Schevenjngen

3 Keratomileusis course Dr Krumeich Room Schevenjngen

4 Laser course Dr Aron-Rosa Room Neuchatel

The session on epikeratoplasty presented different studies of preservation of donor lenticules. If the epithelium is left intact in non-freeze preparation techniques, it will tend to migrate around the lenticule which could potentially lead to the presence of epithelium within an optical interface.

Dr Joyeux presented his clinical results of periocular injection of a combination of insulin, an unknown vasodilator, and calcitonin to reverse the onset of presbyopia. In 100 patients with a 4-month follow-up, 61% were said to have improved slightly, 17% to improve significantly, and 22% to have no change.

Several surgical courses took place on Sunday, June 4. The fourth meeting of the society will take place in Florence in 1990 under the direction of Dr Lucio Buratto.

REFERENCES

1. Agard DA. Optical sectioning microscopy: cellular architecture in three dimensions. Ann New York Acad Sci. 1984; 191-219.

2. Baer SC. (1970). U.S. Patent 3,547,512 Optical apparatus providing focal-plane-specific iUumination.

3. Corle TR, Chou CH, Kino GS. Depth response of confocal optical microscopes. Optics Letters. 1986; 11:770-772.

4. Davidovits P, Egger MD. Scanning laser microscope for hiological investigations. Applied Optics. 1971; 10:1615-1619.

5. Dilly PN. Tandem scanning reflected light microscopy of the cornea. Scanning. 1988; 10:153-156.

6. Egger MD, Petran M. New reflected-light microscope for viewing unstained brain and ganglion cells. Science. 1967; 157:305-307.

7. Gallagher B, Maurice D. Striations of light scattering in the corneal stroma. J Ultrastructure Res. 1977; 61:100-114.

8. Goldstein S. A no-moving parts video rate laser beam scanning type 2 confocal reflected/transmission microscope. J Microscopy. 1989; 153, pt. 2, RP-I.

9. Jester JV, Cavanagh HD, Lemp MA. In vivo confocal imaging, of the eye use tandem scanning confocal microscopy in: Proceedings of the 46th annual meeting of the Electron Microscopy Society of American Ed. G. W. Bailey, San Francisco, 56-57.

10. Jester JV, Cavanagh, HD, Lemp, MA. Confocal microscopic imaging of the living eye with the tandem scanning confocal microscope. In: Noninvasive Diagnostic Techniques in Ophthalmology, B.R. Masters, Ed. New York: Springer- Verlag, in press.

11. Koester CJ. Scanning mirror microscope with optical sectioning characteristics: applications in ophthalmology. Appl Opt. 1980; 19:1749-1757.

12. Koester CJ, Roberts CW, Donn A, Hoefle FB. Wide field specular microscopy. Clinical and research applications. Ophthalmology. 1980; 87:849-860.

13. Lemp MA, Duly PN, Boyde A. Tandem-scanning (confocal) microscopy of the full-thickness cornea. Cornea. 1986; 4:205-209.

14. Masters BR. Effects of contact lenses on the oxygen concentration and epithelial mitochondrial redox state of rabbit cornea measured noninvasively with an optically sectioning redox fluorometer microscope. In: The Cornea: Transactions of the World Congress on the Cornea III, ed. H.D. Cavanagh, 1988; Raven Press, New York, 281-286.

15. Masters BR. Optically sectioning ocular fluorometer microscope: applications to the cornea. SPIE Proceedings: Timeresolved laser spectroscopy in biochemistry, 1988; 909:342-348.

16. Masters BR. Scanning microscope.for optically sectioning the living cornea. In: Scanning Imaging, (T.Wilson, ED.) Proc. SPIE, vol. 1028, SPUE Proceedings 1989, p 133-143.

17. Masters BR. Confocal microscopy of ocular tissue. In: Confocal Microscopy, T. Wilson, ed.; London, Academic Press, in press.

18. Masters BR, Kino GS. Confocal Microscopy of the Eye. In: Noninvasive Diagnostic Techniques in Ophthalmology, B.R. Masters, Ed. New York: Springer- Verlag, in press.

19. Maurice D. A scanning slit microscope. Invest Ophthalmol Vis Sci. 1974; 13:1033-1037.

20. Petran M, Hadravsky M, Benes J, Boyde A. In vivo microscopy using the tandem scanning microscope. Ann New York Acad Sci. 1984; 440-447.

21. Petran M, Hadravsky M, Boyde A. The tandem scanning reflected light microscope. Scanning. 1985; 7:97-108.

22. Webb H, Hughes GW, Delori FC. Confocal scanning laser ophthalmoscope. Applied Optics. 1987; 26:1492-1499.

23. Xiao GQ, Corle TR, Kino GS. Real-time confocal scanning; optical microscope. Appl Phys Lett. 1988; 53(8):716-718.

10.3928/1081-597X-19890901-11

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