Journal of Refractive Surgery

Review 

Surgical Procedures Performed After Refractive Surgery

Perry S Binder, MD, FACS; Kevin H Charlton, MD, FACS

Abstract

ABSTRACT

Background: Refractive surgical procedures have been performed for over one decade. The complications that cause visual disability are abnormalities in wound healing, residual ametropia, and/or severe irregular astigmatism. Many of these complications can be manifested clinically in terms of visually disabling problems (loss of best-corrected vision, glare, monocular diplopia, etc). Some of these complications require additional standard ophthalmic or refractive surgical procedures to restore vision. However, since these secondary procedures have been performed in only a few cases, we know little about their outcome.

Methods: We report the histopathologic analysis of 132 cases that have undergone a secondary surgical procedure following a primary keratorefractive procedure. We attempt to correlate the problems encountered with such secondary intervention with histopathologic information obtained from specimens that have been submitted to our pathology laboratory and that had undergone secondary surgical procedures.

Results: Many specimens displayed abnormalities in wound healing associated with visual difficulties such as loss of best corrected acuity, glare, and under- and overcorrection. A short time from the initial procedure to the time of secondary intervention was common.

Conclustions: The combination of a secondary surgical or keratorefractive procedure can produce unpredictable retractive results. Judicious application of a refractive procedure and an appropriate time period before a second procedure is performed may reduce unexpected refractive complications. [Refract Corneal Surg 1992;8:61-74.)

Abstract

ABSTRACT

Background: Refractive surgical procedures have been performed for over one decade. The complications that cause visual disability are abnormalities in wound healing, residual ametropia, and/or severe irregular astigmatism. Many of these complications can be manifested clinically in terms of visually disabling problems (loss of best-corrected vision, glare, monocular diplopia, etc). Some of these complications require additional standard ophthalmic or refractive surgical procedures to restore vision. However, since these secondary procedures have been performed in only a few cases, we know little about their outcome.

Methods: We report the histopathologic analysis of 132 cases that have undergone a secondary surgical procedure following a primary keratorefractive procedure. We attempt to correlate the problems encountered with such secondary intervention with histopathologic information obtained from specimens that have been submitted to our pathology laboratory and that had undergone secondary surgical procedures.

Results: Many specimens displayed abnormalities in wound healing associated with visual difficulties such as loss of best corrected acuity, glare, and under- and overcorrection. A short time from the initial procedure to the time of secondary intervention was common.

Conclustions: The combination of a secondary surgical or keratorefractive procedure can produce unpredictable retractive results. Judicious application of a refractive procedure and an appropriate time period before a second procedure is performed may reduce unexpected refractive complications. [Refract Corneal Surg 1992;8:61-74.)

Although refractive surgical procedures have been performed for over 50 years, the modern era of refractive surgery began with the introduction of radial keratotomy to the United States in 1978.1 In the last decade, numerous refractive surgical procedures have been introduced, tested clinically, and have fallen into disuse.2 The most commonly performed and most successful refractive surgical procedure to date is radial keratotomy.3-5 Excimer laser photorefractive keratectomy has become the newest refractive surgical modality to undergo clinical investigation.6

The complications following refractive surgery that cause visual disability are residual ametropia and severe irregular astigmatism (Table 1). These and other complications are thought to be related to abnormalities in corneal wound healing.2,7-9 Most of the optical complications are correctable with spectacles and/or contact lenses, but wound-healing problems are not easily correctable and may require additional surgery. Following successful keratorefractive surgery, patients are now developing common aging changes, such as cataract formation. New and unanticipated technical difficulties are being encountered as surgical procedures are performed following keratorefractive surgery. This article describes, to our knowledge for the first time, a review of the types of procedures that can be performed following a refractive surgical procedure. We also analyze histopathologic specimens that have been obtained following secondary surgical procedures to help us understand the mechanism(s) of complications following such secondary surgery.

Table

Table 1Complications Following Refractive Surgery

Table 1

Complications Following Refractive Surgery

MATERIALS AND METHODS

One hundred thirty-two specimens were received in the Ophthalmology Research Laboratory as whole eyes, as corneoscleral rims, as corneal buttons in various fixatives, as paraffin-embedded specimens, and in two cases, in histologic section. Specimens were received between 1978 and 1991. Upon receipt, the specimens were photographed with an overview dissecting microscope at magnifications between 6 X and 20x. Hand drawings of the specimens were entered into the laboratory notebook along with any clinical data. The submitting surgeons were subsequently sent a questionnaire to obtain information about each specimen. The specimens were then processed for a correlative light, scanning, and transmission electron microscopy using previously described morphologic techniques (Binder et al, unpublished data).2-10 Table 2 fists the types and number of specimens that we have examined.

RESULTS

Based on our review of the literature and our specimen database, we have been able to produce an outline of surgical procedures that have either been performed or that theoretically may be performed following refractive surgery (Table 3).

Table

Table 2Refractive Surgery Specimens Studied 1978 to 1991

Table 2

Refractive Surgery Specimens Studied 1978 to 1991

Radial Keratotomy

Repeat Radial and /or Repeat Astigmatic Keratotomy. Deepening of primary incisions and/or placement of additional incisions are employed for undercorrection. Secondary astigmatic procedures are employed in cases of spherical operations that have developed excessive astigmatism, in cases of astigmatic keratotomy with undercorrection of the astigmatic error, or in cases that developed a significant shift in the astigmatism axis. We have previously studied reoperated keratotomy wounds in a monkey model11 and in a clinical specimen that underwent astigmatic and radial keratotomy following a corneal transplant.12 It is not yet clear whether wound healing is different following repeat surgery compared to primary surgery.

Epikeratoplasty Following Radial Keratotomy for Under- or Overcorrection. There have been several oral presentations, but to our knowledge, no published reports of the use of epikeratoplasty for a significant spherical under- and overcorrection following radial keratotomy. A hyperopic epikeratoplasty procedure can be performed following an overcorrection with a piano lenticule or a convex (plus-powered) lenticule (Fig 1).

CASE REPORT

Case 1. A 37-year-old man underwent bilateral, 8-incision radial keratotomy procedures between September 1985 and January 1986. Because of an overcorrection in the right eye, a running, pursestring suture was used.13 Because of a suture erosion and failure of subsequently placed interrupted sutures to correct the hyperopia, he underwent an epikeratoplasty procedure (Epi #1) using a +3.75diopter lenticule in March 1988. The eye developed a severe overcorrection with epithelial interface ingrowth, necessitating a lenticule exchange (Epi #2) with a piano powered lenticule in September 1988. He recovered 20/25 acuity with spectacles (Table 4).

Table

Table 3Outline of Theoretical and Actual Surgical Procedures Performed Following Refractive Surgical Procedures

Table 3

Outline of Theoretical and Actual Surgical Procedures Performed Following Refractive Surgical Procedures

Corneal Transplant Following Radial Keratotomy. Several surgeons have performed corneal transplantation following radial and/or astigmatic keratotomy.9,2'14'15 During surgery, the recipient wounds may open, making wound closure difficult. X-shaped sutures have been used to close each of the radial incisions. The advantage of the corneal transplant is primarily to restore best corrected vision, but if an oversized donor button is used, the eye will usually return to the preradiai keratotomy myopic refraction (unpublished data). A very unusual case report documented the accidental transplantation of a donor eye that had previously undergone a radial keratotomy.16 Our laboratory has also seen a similar case (unpublished data). A careful historical screening of the donor or, when that is not possible, the slit-lamp examination of the cornea at the eye bank will prevent such an occurrence.

Wound Repair for Overcorrections or Traumatic Rupture. Starling and Hofmann13 and Lindquist et al17 have published techniques for suturing corneal wounds for cases that have been overcorrected following radial keratotomy. The results of these procedures are dependent upon wound healing and are consequently unpredictable. Repair of traumatic wound rupture following radial keratotomy has also been reported.18 Such cases are extremely difficult to repair due to numerous and irregular lacerations that can occur with the trauma.

Keratomileusis After Radial Keratotomy. Myopic keratomileusis has been used for undercorrection and hyperopic keratomileusis for overcorrection following radial keratotomy.10-19 The procedure is technically difficult because the microkeratome must cut across radial incisions which causes the keratotomy wounds in the excised cap to splay open, preventing its use in a homoplastic procedure. The base of the keratomileusis wound will contain some of the radial incisions which may open. There is no laboratory or clinical evidence to support the use of keratotomy surgery simultaneously with keratomileusis.

Figure 1: Corneal button obtained after hyperopic epikeratoplasty performed 2 years after several radial keratotomy procedures for overcorrection and loss of best corrected acuity. A slightly thickened epithelium In the visual axis overlies focal breaks in the lentlcule's Bowman's layer (*). The lenticule stroma appears to be normally populated with keratocytes. Two keratotomy incisions are present In close proximity (solid arrows), creating a focal "island" of the host's Bowman's layer. A blood vessel is present immediately above one incision (open arrow). (Mallory's azure II, methylene blue, basic fuchsin stain, ? 150).Table 4Case 1Table 5Case 2

Figure 1: Corneal button obtained after hyperopic epikeratoplasty performed 2 years after several radial keratotomy procedures for overcorrection and loss of best corrected acuity. A slightly thickened epithelium In the visual axis overlies focal breaks in the lentlcule's Bowman's layer (*). The lenticule stroma appears to be normally populated with keratocytes. Two keratotomy incisions are present In close proximity (solid arrows), creating a focal "island" of the host's Bowman's layer. A blood vessel is present immediately above one incision (open arrow). (Mallory's azure II, methylene blue, basic fuchsin stain, ? 150).

Table 4

Case 1

Table 5

Case 2

CASE REPORT

Case 2. A 33-year-old woman underwent a 16incision radial keratotomy in her left eye in July 1980, using razor blade fragments and a 3.00millimeter optical clear zone. Because of undercorrection, she underwent an additional eight incisions with a 3.00-miliimeter clear zone in March 1985. Because there was no improvement in the refractive error, she underwent myopic keratomileusis on February 6, 1986. When last examined August 3, 1988, her uncorrected acuity was greatly improved (Table 5). (The keratometry readings did not correlate with the changes in refraction after the second radial keratotomy.)

Cataract Surgery Following Radial Keratotomy. In 1986, Cottingham (unpublished data) reported a series of cataract extractions foUowing radial keratotomy performed by Ralph Berkeley, MD. They encountered problems calculating the intraocular lens (IOL) implant power. Cottingham recommended using the preradiai keratotomy keratometry readings to calculate lens implant powers. Holladay20 subsequently recommended performing a refraction over a hard contact lens of known curvature and power, to determine the effective corneal power after radial keratotomy. Koch and coworkers21 reported that following cataract surgery in four eyes that had previously undergone radial keratotomy, the corneas flattened excessively, creating significant hyperopia. They considered the Birkhorst and Holladay formulas to most accurately predict IOL power. They21 and Nordan22 calculated effective corneal power by subtracting the refractive change following radial keratotomy from the preoperative corneal power measured with the keratometer. Other surgeons (unpublished data) have also reported that such corneas tend to swell more than usual for a similar amount of surgical trauma, but if the proper keratometry readings are calculated, the refractive errors can be within 2.00 diopters of emmetropia.

Table

Table 6Case 3

Table 6

Case 3

CASE REPORT

Case 3. A 50-year-old man underwent an 8-incision radial keratotomy procedure 9 years prior to developing a visually significant cataract. The SRK-T formula predicted that a 23.00-diopter IOL would produce a spherical equivalent of -3.71 D and the Holladay formula predicted -3.73 D with the same IOL using the actual K-readings. Using the adjusted average K minus the refractive change in diopters that occurred after the radial keratotomy, the SRK-T predicted a final refraction of -2.35 D and the Holladay predicted - 2.37 D. Ihirty-two weeks postoperative using the 23.00-diopter IOL, the spherical equivalent was -2.88 D (Table 6).

Excimer Laser Photoablation Following Radial Keratotomy. This procedure could be indicated for a significant undercorrection. It is not clear how the cornea might respond to photorefractive keratectomy following radial keratotomy. McDonnell and SaIz have separately performed such a procedure (personal communication, October 12, 1990). Since keratotomy wounds are slow to heal,10 one might be concerned about extending the ablation zone outside the optical clear zone, which could potentially open the keratotomy incisions.

Figure 2: Silt-lamp view of a myopic epikeratoplasty performed over a myopic epikeratoplasty for severe undercorrection. The host's stroma appears to be optically lucent (black arrow) In fhe posterior part of the silt photo. The first myopic epikeratoplasty (MyEKP) is somewhat opaque in appearance (white arrow head). Overlying the first MyEKP, one can see the second EKP In the superior part of the slit immediately below the eyelid margin (thick white arrow).Table 7Case 4

Figure 2: Silt-lamp view of a myopic epikeratoplasty performed over a myopic epikeratoplasty for severe undercorrection. The host's stroma appears to be optically lucent (black arrow) In fhe posterior part of the silt photo. The first myopic epikeratoplasty (MyEKP) is somewhat opaque in appearance (white arrow head). Overlying the first MyEKP, one can see the second EKP In the superior part of the slit immediately below the eyelid margin (thick white arrow).

Table 7

Case 4

Radial Thermokeratoplasty Following Radial Keratotomy. Radial thermokeratoplasty, which is a modification of thermokeratoplasty, has come and gone in a few short years.23-24 Thermal cauteryproducing collagen shrinkage has been used to treat astigmatism and keratoconus. We are unaware of the application of thermokeratoplasty for treating under- or overcorrections following radial keratotomy.

Epikeratoplasty

Repeat Epikeratoplasty: Epikeratoplasty Over an Epikeratoplasty. The most common operations following epikeratoplasty are either a repeat operation or a removal. Repeat procedures are most commonly performed for significant under- or overcorrections25 or for wound healing problems.26'27 The procedures are technically very simple and are usually successful in terms of lenticule clarity, but can be complicated by loss of best corrected vision.

Figure 3: Corneal button obtained 4 years after myopic epikeratoplasty which was performed for overcorrection after extracapsular cataract surgery with an intraocular lens implant. The lentlcule's Bowman's layer Is thrown into numerous folds at the site of the peripheral wound in the host. In this area, the surface epithelium has increased in thickness to smooth out the surface Irregularity created (arrow). The normal lamellar pattern of the host stroma is severely disrupted in this area('). A piece of the host's Bowman's layer is seen at the edge of the lenticule (small arrow). It assumes a flat orientation across the visual axis to the right. The lenticule is rucked in and under the host stroma In the area of several bends in the donor Bowman's layer (white arrows) (Mallory's azure II, methylene blue, basic fuchsin stain, ? 135).Table 8Case 5

Figure 3: Corneal button obtained 4 years after myopic epikeratoplasty which was performed for overcorrection after extracapsular cataract surgery with an intraocular lens implant. The lentlcule's Bowman's layer Is thrown into numerous folds at the site of the peripheral wound in the host. In this area, the surface epithelium has increased in thickness to smooth out the surface Irregularity created (arrow). The normal lamellar pattern of the host stroma is severely disrupted in this area('). A piece of the host's Bowman's layer is seen at the edge of the lenticule (small arrow). It assumes a flat orientation across the visual axis to the right. The lenticule is rucked in and under the host stroma In the area of several bends in the donor Bowman's layer (white arrows) (Mallory's azure II, methylene blue, basic fuchsin stain, ? 135).

Table 8

Case 5

CASE REPORT

Case 4. A 20-year-old woman developed severe giant papillary conjunctivitis with contact lenses. She underwent bilateral, myopic epikeratoplasty procedures between January and June 1989 for high myopia. The left eye procedure was complicated by perforation of the host cornea with the HessburgBarron trephine which necessitated deep placement of the lenticule wing in the peripheral host corneal stroma. The refraction subsequently regressed in her left eye. In September 1990, a planned lenticule exchange failed because the epikeratoplasty button could not be removed. Consequently, a second myopic epikeratoplasty lenticule was placed over the first (Fig 2). When she was last seen, the lenticules were both clear (Table 7).

It is possible that the perforation and deep placement of the first lenticule created the strong scar between the lenticule and host. Immediately prior to the second surgery, the surgeon could not identify two Bowman's layers centrally, but following the repeat additional epikeratoplasty, he was able to discern the host Bowman's membrane and the two donor Bowman's membranes (Fig 2). The preoperative keratometry and refraction were very similar to those at the time of reoperation.

Removal of Epikeratoplasty With or Without Secondary Sewn-In Posterior Chamber Lens Implants. Initially, it was thought that removal of an epikeratoplasty lenticule was completely reversible, but studies have demonstrated that morphologic changes can take place in the host's Bowman's layer.28 Some authors have reported increased myopia following epikeratoplasty lenticule removal.26,28"30 The increase in corneal steepening is thought to be associated with the circular trephination step. Some infections in the donor could produce opacification in the host tissue.31 In most cases, however, the host epitheHum rapidly resurfaces the area of excision after lenticule removal, allowing the cornea to return to its preoperative clarity. The recent successful application of sewn-in posterior chamber lens implants have reduced the number of cases undergoing aphakic epikeratoplasty procedures.

Corneal Transplant Following Epikeratoplasty. Lembach and coworkers32 found that 12 of 33 eyes needed contact lenses following epikeratoplasty for keratoconus, and one additional eye required a corneal transplant. One common indication for corneal transplantation following epikeratoplasty is inadequate visual acuity following epikeratoplasty for keratoconus.3335 The second most common indication is an infection following epikeratoplasty.25,26*27 Transplant procedures, after an epikeratoplasty procedure, are technically the same, as for any standard corneal transplant operation, as long as the diameter of the trephination of the recipient is the same or greater than that performed for the epikeratoplasty procedure (Fig 3).

Figure 4: Corneal button obtained 24 months after an epikeratoplasty (using a fresh-frozen donor) for keratoconus. Astigmatic keratotomy had also been performed at 8 and 10 monihs after the epikeratoplasty. The overlying epithelium is edematous. One keratotomy is visible with an intact epithelial plug which Is surrounded by active keratocytes (Mallory's azure II, methylene blue, basic fuchsin stain, ? 150). Electron microscopy (inset) demonstrated the epithelial plug (E) to be surrounded by an intact basal lamina with hemldesmosomes. The lenticule (L) was hypocellular compared to the host (uranyl acetate, lead citrate stain, ? 37 500).Table 9Case 6

Figure 4: Corneal button obtained 24 months after an epikeratoplasty (using a fresh-frozen donor) for keratoconus. Astigmatic keratotomy had also been performed at 8 and 10 monihs after the epikeratoplasty. The overlying epithelium is edematous. One keratotomy is visible with an intact epithelial plug which Is surrounded by active keratocytes (Mallory's azure II, methylene blue, basic fuchsin stain, ? 150). Electron microscopy (inset) demonstrated the epithelial plug (E) to be surrounded by an intact basal lamina with hemldesmosomes. The lenticule (L) was hypocellular compared to the host (uranyl acetate, lead citrate stain, ? 37 500).

Table 9

Case 6

Durrie (personal communication, October 28, 1989) performed an unusual case of an epikeratoplasty sewn on top of a donor cornea, and the entire donor cornea with the epikeratoplasty lenticule attached was transplanted as a standard corneal transplant. The case was performed because of the need to correct a corneal leukoma and aphakia in a case that was not a candidate for a sewn-in lens implant at keratoplasty.

CASE REPORT

Case 5. A 74-year-old woman underwent a left extracapsular cataract extraction and intraocular lens implant in October 1983. The procedure was complicated by an overcorrection of 10.00 D of myopia. In October 1985, she underwent a myopic epikeratoplasty procedure. In December 1986, the spherical equivalent was -9.50 (6/9) in the unoperated right eye and was - 4.25 (6/24) in the operated left eye. All sutures had been removed and the lenticule and posterior capsule were clear. There was no change in the findings in October 1989. On December 21, 1989, she underwent a left corneal transplant with an 8-millimeter donor and recipient. When last examined in June 1990, the best corrected acuity was 20/30 (6/9) (Table 8).

Cataract Surgery Following Epikeratoplasty. These procedures may be indicated for patients who have had a previous myopic epikeratoplasty and who have developed a cataract. Since one is able to eliminate myopia following lens implantation for cataract surgery, the necessity for the original myopic epikeratoplasty procedure is eliminated when an eye undergoes cataract surgery. The epikeratoplasty lenticule can be removed prior to cataract surgery and the corneal curvature allowed to return to stable readings, which can then be utilized for lens implant power calculations. If one chooses to leave the myopic epikeratoplasty lenticule in-situ, then the problem of calculating corneal power becomes the same as for calculating effective corneal power following radial keratotomy (see the section on Cataract Surgery Following Radial Keratotomy). The operation is technically no more difficult than standard cataract surgery, assuming the optics of the interface are good.

Figure 5: Corneal button obtained 45 days after an excimer laser photoablation over an undercorrected myopic epikeratoplasty that had been performed 4 years previously. (A) At low power, the thickened surface epithelium appears to taper at the site of energy delivery (small arrow) toward the visual axis to the right. The epithelium Is partially removed in the adjacent area. Two small "Islands" of epithelium remain over the ablated area (large arrows). Further to the right, the ablated stoma is seen to be devoid of Bowman's layer and epithelium (Mallory's azure II, methylene blue, basic fuchsin stain, ? 150). (B) (Area in black brackets in 5A). Transmission micrograph Jn ablated stroma. There is a sharp demarcation between the stroma and the edge of the ablated collagen as has been previously published by others. The abnormal appearance of the underlying stroma is probably due to the cryopreservation technique used to prepare the tissue (uranyl acetate, lead citrate stain, ? 8500). (C) (Area in white brackets in 5A) Low power transmission electron micrograph of tapered edge of the ablated epithelium. Note the intact epithelial cell nucleus (arrow). The surface of the lenticule's Bowman's layer appears to be covered by a 0.50-micron thick condensation of collagen that appears to be continuous under the epithelium (*) (uranyl acetate, lead citrate stain, ? 8500).

Figure 5: Corneal button obtained 45 days after an excimer laser photoablation over an undercorrected myopic epikeratoplasty that had been performed 4 years previously. (A) At low power, the thickened surface epithelium appears to taper at the site of energy delivery (small arrow) toward the visual axis to the right. The epithelium Is partially removed in the adjacent area. Two small "Islands" of epithelium remain over the ablated area (large arrows). Further to the right, the ablated stoma is seen to be devoid of Bowman's layer and epithelium (Mallory's azure II, methylene blue, basic fuchsin stain, ? 150). (B) (Area in black brackets in 5A). Transmission micrograph Jn ablated stroma. There is a sharp demarcation between the stroma and the edge of the ablated collagen as has been previously published by others. The abnormal appearance of the underlying stroma is probably due to the cryopreservation technique used to prepare the tissue (uranyl acetate, lead citrate stain, ? 8500). (C) (Area in white brackets in 5A) Low power transmission electron micrograph of tapered edge of the ablated epithelium. Note the intact epithelial cell nucleus (arrow). The surface of the lenticule's Bowman's layer appears to be covered by a 0.50-micron thick condensation of collagen that appears to be continuous under the epithelium (*) (uranyl acetate, lead citrate stain, ? 8500).

Radial or Astigmatic Keratotomy Following Epikeratoplasty. The most common application of keratotomy incisions following epikeratoplasty are for high astigmatic errors.36 A recent theoretical case example has been discussed by several experts.37 Eelaxing incisions can be placed close to the donor/ recipient junction, just as are performed for relaxing incisions for astigmatism following corneal transplantation.38 Based on our personal experience, the donor tissue in epikeratoplasty specimens responds unpredictably to keratotomy incisions. The major complication following such keratotomy incisions is poor wound healing (Fig 4).

CASE REPORT

Case 6. A 28-year-old woman underwent an epikeratoplasty for keratoconus in July 1986, using a freshfrozen donor cornea. Three months later, she saw 20/25 with spectacles, but only 20/50 with a soft toric lens. In December 1986, arcuate relaxing incisions were placed inside the epikeratoplasty wound. In February 1987, a trapezoidal keratotomy was added to achieve 100% depth of the lenticule. Because there was no effect on the uncorrected acuity and astigmatism, a corneal transplant was performed in January 1988 (Fig 4). Following the transplant, she recovered 20/25 best corrected acuity (Table 9).

Figure 5: Corneal button obtained 45 days after an excimer laser photoablation over an undercorrected myopic epikeratoplasty that had been performed 4 years previously. (A) At low power, the thickened surface epithelium appears to taper at the site of energy delivery (small arrow) toward the visual axis to the right. The epithelium Is partially removed in the adjacent area. Two small "Islands" of epithelium remain over the ablated area (large arrows). Further to the right, the ablated stoma is seen to be devoid of Bowman's layer and epithelium (Mallory's azure II, methylene blue, basic fuchsin stain, ? 150). (B) (Area in black brackets in 5A). Transmission micrograph Jn ablated stroma. There is a sharp demarcation between the stroma and the edge of the ablated collagen as has been previously published by others. The abnormal appearance of the underlying stroma is probably due to the cryopreservation technique used to prepare the tissue (uranyl acetate, lead citrate stain, ? 8500). (C) (Area in white brackets in 5A) Low power transmission electron micrograph of tapered edge of the ablated epithelium. Note the intact epithelial cell nucleus (arrow). The surface of the lenticule's Bowman's layer appears to be covered by a 0.50-micron thick condensation of collagen that appears to be continuous under the epithelium (*) (uranyl acetate, lead citrate stain, ? 8500).

Figure 5: Corneal button obtained 45 days after an excimer laser photoablation over an undercorrected myopic epikeratoplasty that had been performed 4 years previously. (A) At low power, the thickened surface epithelium appears to taper at the site of energy delivery (small arrow) toward the visual axis to the right. The epithelium Is partially removed in the adjacent area. Two small "Islands" of epithelium remain over the ablated area (large arrows). Further to the right, the ablated stoma is seen to be devoid of Bowman's layer and epithelium (Mallory's azure II, methylene blue, basic fuchsin stain, ? 150). (B) (Area in black brackets in 5A). Transmission micrograph Jn ablated stroma. There is a sharp demarcation between the stroma and the edge of the ablated collagen as has been previously published by others. The abnormal appearance of the underlying stroma is probably due to the cryopreservation technique used to prepare the tissue (uranyl acetate, lead citrate stain, ? 8500). (C) (Area in white brackets in 5A) Low power transmission electron micrograph of tapered edge of the ablated epithelium. Note the intact epithelial cell nucleus (arrow). The surface of the lenticule's Bowman's layer appears to be covered by a 0.50-micron thick condensation of collagen that appears to be continuous under the epithelium (*) (uranyl acetate, lead citrate stain, ? 8500).

Excimer Laser Photoablation After Epikeratoplasty. Significant under- and overcorrections are common following epikeratoplasty procedures.39 Theoretically, one could consider using the excimer laser to "fine tune* corneal curvature following epikeratoplasty. Recently, Thompson et al40 have suggested the possibility of using synthetic epikeratoplasty lenticules and later fine tuning the results with the excimer laser.

CASE REPORT

Case 7. A 22-year-old man underwent a myopic epikeratoplasty in May 1985. Because of an undercorrection, a second myopic epikeratoplasty was performed in November 1985. The patient complained of glare and fluctuation in acuity. The refractive error was recorded between - 5.00 D and -8.00 D over the next 2 years. In August 1989, an excimer laser photoablation was attempted to correct 6.00 D. Initially, the refractive error was corrected to piano, but later regressed to the preoperative levels. The epikeratoplasty lenticule was removed on September 30, 1990 (Fig 5).

Table

Table 10Case 8

Table 10

Case 8

This case suggests that previously frozen and/or freeze-dried tissue may not respond predictably to photoablation.

Keratomileusis

Radial and ior Astigmatic Keratotomy Following Keratomileusis. The most common complication of keratomileusis, in our opinion, is irregular astigmatism at the optical interface. This type of astigmatism is not amenable to keratotomy incisions. Nevertheless, surgeons have utilized radial and/or astigmatic patterns in the host bed at the time of keratomileusis, or in the keratomileusis lenticule following surgery to correct astigmatism.41 Some cases have simply had the lenticule lifted off and immediately replaced in hopes of correcting astigmatism.

CASE REPORTS

Case 8. A 31-year-old man underwent bilateral myopic keratomileusis between March and August, 1984, for high myopia. Because of a severe undercorrection, in September 1985 he underwent an 8incision radial keratotomy with a 4 x 5-millimeter oval optical clear zone, at a central depth of 0.51 mm, and a peripheral redeepening at 0.58 mm. Following the second procedure, the uncorrected acuity improved.

In this ease, eight incisions reduced the spherical equivalent from -2.50 D to -0.50 D5 only a 2.00diopter change for maximum radial keratotomy surgery. This result suggests that the effect of radial keratotomy after keratomileusis may not be as great as the same radial keratotomy procedure performed in a previously unoperated eye (Table 10).

Figure 6: Myopic keratomileusis lenticule [ obtained 46 months after surgery and 26 months after a trapezoidal keratotomy. The epithelium is thicker towards the limbus on the right, but has thinned immediately to the left at the probable site of the insertion of the lenticule (arrow). It then thickens again towards the visual axis to the left. A full-thickness keratotomy wound is seen on the left containing a small epithelial plug (small arrow). The Incision appears to contain epithelial cell remnants in the center (*). (Mallory's azure II, methylene blue, basic fuchsin stain, ? 135).Table 11Case 10

Figure 6: Myopic keratomileusis lenticule [ obtained 46 months after surgery and 26 months after a trapezoidal keratotomy. The epithelium is thicker towards the limbus on the right, but has thinned immediately to the left at the probable site of the insertion of the lenticule (arrow). It then thickens again towards the visual axis to the left. A full-thickness keratotomy wound is seen on the left containing a small epithelial plug (small arrow). The Incision appears to contain epithelial cell remnants in the center (*). (Mallory's azure II, methylene blue, basic fuchsin stain, ? 135).

Table 11

Case 10

Case 9. A 37-year-old woman underwent a myopic keratomileusis in April 1983 for - 12.50 D of myopia. The postoperative refraction was - 1.00 + 4.00 ? 64°. Because of residual astigmatism, a trapezoidal keratotomy was performed in December 1984. The postkeratotomy refraction was +3.00 + 2.75 X 171°. Because of the residual astigmatism and poor uncorrected acuity, a repeat myopic keratomileusis was performed in February 1987 (Fig 6).

Repeat Keratomileusis. Indications for repeat myopic keratomileusis are usually significant underand overcorrection. The procedure is not technically difficult, but is complicated by a high incidence of irregular astigmatism, significant under- and overcorrections, and loss of best corrected acuity due to interface opacification and haze.7 Previous morphologic studies of such specimens have demonstrated thickening (hyperplasia) of the epithelium over the visual axis in the area of stromal excision. This is the very problem facing the excimer laser procedures; that is, epithelial remodeling in the excised area which reduces the effect of the surgery.

CASE REPORT

Case 10. A 28-year-old male underwent a 16incision radial keratotomy in 1980. Because of significant undercorrection, he had his first myopic keratomileusis in October 1982. The lenticule was removed and rotated in November 1982 due to high astigmatism. A second myopic keratomileusis was performed in March 1983 because of interface astigmatism. This procedure created high myopia and astigmatism with decreased best corrected acuity. A third myopic keratomileusis was performed in January 1984, which also resulted in high astigmatism. A fourth procedure in June 1985 reduced the astigmatism, but due to interface haze and loss of best corrected acuity, a full thickness corneal transplant was performed with recovery of best acuity to 20/30 (Table 11).

There were too many operations5 performed over a short period of time (22 months). If a second procedure didn't improve the refractive error or best corrected acuity, then a hard contact lens should have been attempted until the patient's best corrected acuity demanded an improvement, and at that time a penetrating keratoplasty could be considered.

Corneal Transplant Following Keratomileusis. The indication for corneal transplantation following keratomileusis is loss of best corrected acuity, either through interface opacity, scarring, or irregular astigmatism (see case 10). The procedure is no more technically difficult than any other corneal transplant and has a high degree of success. As with corneal transplants following radial keratotomy, the postoperative refraction will usually return to a myopic level similar to the prekeratomileusis refraction unless the surgeon uses a same size or undersize donor-recipient diameter (Binder PS, unpublished data).42

Cataract Surgery Following Keratomileusis. We are unaware of a published report of cataract surgery following keratomileusis, but the same principles of calculating corneal power apply as are used for radial keratotomy.

Excimer Laser Photoablation Following Keratomileusis. Refractive undercorrection following myopic keratomileusis is not uncommon. Some authors have recommended performing a radial keratotomy after myopic keratomileusis, but it is theoretically possible to use the excimer laser to treat undercorrections as well. McDonnell (personal communication, October 12, 1990) recently performed such an operation.

Previous histopathologic studies of myopic keratomileusis have demonstrated epithelial hyperplasia in the optic zone (Fig 6) which most likely occurred in response to corneal flattening produced by the procedure. Excimer laser photoablation also produces central corneal flattening and, in some cases, epithelial hyperplasia with loss of refractive effect. Subsequent epithelial debridement has been reported to restore the initial refractive correction. The placement of a photoablation in the optical center following myopic keratomileusis could, therefore, be clinically ineffective if epithelial hyperplasia ensues.

Corneal Transplantation

Radial Keratotomy After Corneal Transplantation. Patients who have significant corneal steepening following corneal transplantation have been reported to undergo spherical radial keratotomy procedures. As with other refractive surgical procedures, keratotomy incisions within a transplanted cornea do not usually respond optically or in terms of wound healing as would a healthy unoperated cornea and, consequently, the refractive error following such a procedure would be highly Unpredictable 7-9,17,43-46

Relaxing Incisions and Wedge Resections Following Corneal Transplant. These procedures have been previously reported and reviewed.47

Repeat Corneal Transplant. The most common indications for repeat corneal transplant are donor failure and opacification, but the procedure rarely can be performed for significant refractive errors.48

Cataract and I or Lens Implant Surgery Following Corneal Transplantation. There are two indications that require cataract surgery and corneal transplantation. A patient presenting with a combined corneal leukoma and a cataract could undergo a triple procedure49 and have a 60% to 80% chance of obtaining a refractive error within 2.00 D of emmetropia with a single operation. Alternatively, surgeons have recommended performing the corneal transplant with or without the cataract extraction, but not with the lens implant, and at a later date, performing a secondary implant or a cataract extraction with lens implant.50 Although a greater percentage of eyes can achieve refractions within 2.00 D of emmetropia taking the later approach, there is increased risk of graft opacification. In a very unusual case, a second IOL was implanted in the same eye to correct high residual hyperopia following a triple procedure.51

Excimer Laser Photoablation Following Corneal Transplant. Unexpected steep keratometry readings following oversized corneal transplants can lead to myopic refractive errors (Binder PS, unpublished data). We are aware of one case that had undergone excimer laser photoablation for high myopia following corneal transplantation (Lindstrom, personal communication, July 28, 1990). In that case, the patient did not achieve a significant reduction in myopia. The reason is probably due to the fact that the transplanted cornea and the circumferential transplant wound do not permit the corneal flattening that can normally be achieved in an unoperated cornea.

CASE REPORT

Case 11. A 42-year-old woman had undergone a corneal transplant for keratoconus. The postoperative refraction was - 14.50 + 6.00 X 105° (6/60). With a hard contact lens over refraction, the acuity improved to 6/18. One month following an excimer laser photoablation, the refraction was -1.00 + 0.87 X 108°. At 3 months, the refraction was - 6.25 + 8.00 x 95°, and 9 months after surgery the refraction had regressed to - 15.00 + 5.00 x 90° (case report courtesy of W. Stark, MD and M. Gilbert, MD).

Myopic Epikeratoplasty After Corneal Transplant. Another approach to correcting high myopia associated with unexpected steep keratometry readings is to perform a myopic epikeratoplasty procedure. We are unaware of such a procedure being performed, but would expect it to be technically difficult because of the necessity of a circumferential trephination for the myopic epikeratoplasty procedure over a cornea that already has a circumferential trephination. Goosey and Vila-Coro52 reported performing an aphakic epikeratoplasty procedure following a rotational autokeratoplasty in a 3-year-old without any surgical complications.

Excimer Laser Photoablation

Corneal Transplant Following Excimer Laser Photoablation. Although some degree of corneal haze and/or scarring occurs in most patients following excimer laser photoablation, the best corrected vision is rarely decreased more than one or two lines.6 Technically, a corneal transplant would be easy to perform and the success rate would be very high, although the patient can expect a return of their prelaser refractive error unless the surgeon uses a same-size or undersized donor button.41,42

Cataract Surgery Following Excimer Laser Photoablation. Since so few patients in the United States have undergone excimer laser photoablation, it is likely that no eye has developed a cataract. Nevertheless, the problems of calculating effective corneal power will apply in this instance, just as it does in cataract surgery following any other refractive procedure.

Repeat Excimer Laser Photoablation. The most common complication following excimer laser photoablation is the same as all other refractive surgical procedures: undercorrection. It has been suggested that repeat operations be considered for these significant undercorrected cases. The impact of repeat energy application, to a cornea that has already been stimulated to undergo wound healing, will most likely lead to an increased wound healing response even if frequent application of corticosteroids are used.

Keratomileusis Following Excimer Laser Photoablation. If visually disabling scarring were to occur foUowing excimer laser photoablation, it would involve only the superficial layers of the cornea which could easily be replaced with a donor lenticule. A piano power lenticule could easily be applied in such a case to permit restoration of the preoperative best corrected acuity.

Epikeratoplasty Following Excimer Laser Photoablation. It is not inconceivable that a significant overcorrection could be treated with a hyperopic epikeratoplasty lenticule, whereas a significant undercorrection would probably be left untreated. To our knowledge, this procedure has not been performed.

Radial Keratotomy at the Time of a Refractive Surgical Procedure

Radial Keratotomy Performed in the Host Bed at the Time of Keratomileusis. Although such procedures have been suggested and performed,41 the efficacy has never been proven.

Radial Keratotomy at the Time of Epikeratoplasty. We are unaware that this application of radial keratotomy has been published.

Astigmatic Keratotomy at the Time of Cataract Surgery. Maloney et al53 and Thornton54 have advocated the use of keratotomy incisions primarily for against-the-rule astigmatism at the time of phacoemulsification. Since corneal curvature following phacoemulsification can change and does not stabilize for at least a year, one does not know the final keratometry readings and refractive error that the patient will have until months after surgery. Transverse incisions applied in eyes for the correction of naturally occurring astigmatism are somewhat predictable, but also require several months to achieve their final refractive result.55 Keratotomy procedures performed in older patients achieve greater but more unpredictable results.

Keratotomy procedures are associated with abnormalities in wound healing. Keratotomy procedures performed in a cataract patient who is usually over 50 years of age will also have unpredictable effects. Cataract patients usually receive topical steroids after surgery which can retard wound healing. Therefore, the application of a somewhat unpredictable procedure, in an age group that has unpredictable results with keratotomy procedures, and in an operation that produces minimal corneal edema and requires postoperative steroids which do not produce stable corneal curvatures for months after surgery, does not seem prudent.

Myopic Anterior Chamber Implants

Polymethylmethacrylate minus powered implants have been used to correct high myopia in phakic eyes.56"58 Preliminary studies suggested the implants were well tolerated, but long-term studies have demonstrated progressive endothelial cell loss; lenses are now being removed to prevent further cell loss. In addition to lens removals, we can expect lens exchanges for power adjustment, repair of retinal detachments in these myopic eyes, and, if endothelial cell loss continues, corneal transplantation.

CONCLUSIONS

The major problems associated with refractive surgical procedures are usually under- and overcorrection and wound healing abnormalities that lead to loss of best corrected vision (Table 1). Overcorrection of a preexisting refractive error is the most disconcerting complication to the surgeon and to the patient, and if not amenable to correction with spectacles or contact lenses, may be correctable with additional surgical procedures (Table 2). Because of the known problems associated with surgical procedures in general, and refractive surgical procedures in particular, it is best to avoid the problems of under- and overcorrection in the first place, by improved patient selection, judicious suture removal, judicious use of corticosteroids, and proper application of a refractive surgical procedure to patients with appropriate refractive expectation. To avoid complications, it would probably be best advised to wait until the refractive error has stabilized following the refractive surgical procedure before planning to perform a reoperation.

Based on the results of the pathology specimens that we have examined, major problems occur when surgeons mix various refractive surgical procedures simultaneously or perform them close together in time.2,7-9,12,44,53,59,60 Until which time we are able to improve the predictability of our refractive surgical procedures and control wound healing, we are best advised to carefully select those patients that undergo refractive surgery and perform the minimum refractive surgical procedure necessary. Heroic attempts to correct high ametropias can be fought with significant refractive complications.

REFERENCES

1. Fyodorov S, Durnev V. Operation of doaaged dissection of corneal circular ligament in cases of myopia of mild degree. Ann Ophthalmol. 1979;11:1885-1890.

2. Binder PS. What we have learned about corneal wound healing from refractive surgery. Refract Corneal Surg. 1989;5:98-120.

3. Binder PS. Radial keratotomy in the 1990's and the PERK study. JAMA. 1990;263:1127.

4. Binder PS. Radial keratotomy in America: where are we six years later? Ophthalmology. 1987;105:37-39.

5. Binder PS. The status of radial keratotomy. Arch Ophthalmol. 1984;102:1601-1603.

6. Binder PS. The excimer laser and radial keratotomy - two vastly different approaches for myopia correction. Arch Ophthalmol. In press.

7. Binder PS. Optical problems following refractive surgery. Ophthalmology. 1986;93:739-745.

8. Deg J, Binder PS. Wound healing after astigmatic keratotomy in human eyes. Ophthalmology. 1987;94:1290-1298.

9. Deg J, Zavala E, Binder PS. Delayed corneal wound healing following radial keratotomy. Ophthalmology. 1985;92:734740.

10. Binder PS, Nayak S, Deg J, Zavala E, Sugar J. An ultrastructural and histochemical study of long-term wound healing after radial keratotomy. Am J Ophthalmol. 1987;103:432440.

11. Melles G, Binder PS. A comparison of wound healing in sutured and unsutured corneal wounds. Arch Ophthalmol. 1990;106:1460-1469.

12. Stainer G, Shaw E, Binder PS, Zavala E, Akers P. Histopathology of a case of radial keratotomy. Arch Ophthalmol. 1982;100:1473-1477.

13. Starling J, Hofmann RF. A new surgical technique for the correction of hyperopia after radial keratotomy: an experimental model. Journal of Refractive Surgery. 1986;2:9-14.

14. Karr D, Grutzmacher R, Reel M. Radial keratotomy complicated by sterile keratitis and corneal perforation: histopathologic case report and review of complications. Ophthalmology. 1985;92:1244-1248.

15. Beatty R, Robin J, Schanzlin D. Penetrating keratoplasty after radial keratotomy. Journal of Refractive Surgery. 1986;2:207-214.

16. Angulo E. Accidental grafting of a donor cornea with radial keratotomy in a keratoconus patient. Refract Corneal Surg. 1989;5:198-201.

17. Lindquist T, Williams P, Lindstrom R. Management of overcorrection following astigmatic keratotomy. Journal of Refractive Surgery. 1988;4:218-221.

18. Binder PS, Waring GO, Arrowsmith P, Wang C. Histopathology of traumatic corneal rupture after radial keratotomy. Arch Ophthalmol. 1988;106:1584-1590.

19. Swinger C, Barker B. Myopic keratomileusis following radial keratotomy. Journal of Refractive Surgery. 1985;1:53-55.

20. Holladay J. Consultations in refractive surgery. Refract Corneal Surg. 1989;5:203.

21. Koch D, Liu J, Hyde L, et al. Refractive complications of cataract surgery after radial keratotomy. Am J Ophthalmol. 1989;108:676-682.

22. Nordan L. Quantifiable astigmatism correction: concepts and suggestions. J Cataract Refract Surg. 1986;12:507-518.

23. Caster A. The Fyodorov technique of hyperopia correction by thermal coagulation: a preliminary report. Journal of Refractive Surgery. 1988;4:105-108.

24. McDonnell P. Radial thermokeratoplasty for hyperopia. I. The need for prompt prospective investigation. Refract Corneal Surg. 1989;5:50-52.

25. Grabner G. Complications of epikeratophakia. Journal of Refractive Surgery. 1988;4:96-104.

26. Binder PS, Baumgartner S, Zavala E, et al. Why do some epikeratoplasties Ml? Arch Ophthalmol. 1987;105:63-69.

27. Frangieh G, Kenyon K, Wagoner M, et al. Epithelial abnormalities and sterile ulceration of epikeratoplasty grafts. Ophthalmology. 1988;95:213-227.

28. Price F, Binder PS. Scarring of recipient cornea following epikeratoplasty. Arch Ophthalmol. 1987;105:1556-1560.

29. Binder PS, Baumgartner S, Zavala E, Deg J. The histopathology of a case of epikeratophakia. Arch Ophthalmol. 1985;103:1357-1363.

30. Neumann A, McCarthy G, Sanders D. Delayed regression of effect in myopic epikeratophakia vs myopic keratomileusis for high myopia. Refract Corneal Surg. 1989;5:161-166.

31. Colin J, Mimouni F, Robinet A, Conrad H, Mader P. The surgical treatment of high myopia: comparison of epikeratoplasty, keratomileusis and minus power anterior chamber Lenses. Refract Corneal Surg. 1990;6:245-251.

32. Lembach R, Lass J, Stocker E, Keates R. The use of contact lenses after keratoconic epikeratoplasty. Arch Ophthalmol. 1989;107:364-368.

33. Goodman G, Werblin T, Pfeiffer R. Failed epikeratophakia for keratoconus. Cornea. 1986;5:29-34.

34. Zavala E, Binder PS, Rock M. Light and electron microscopy of nine failed epikeratoplasty for keratoconus cases. Ophthalmology. 1990;97:137.

35. Kraff C, Peng Y, Robin J. A clinicopathologic correlation of a long-term failed epikeratoplasty for keratoconus. Invest Ophthalmol Vis Sci. 1990;31:30.

36. Arffa R, Klyce S, Busin M. Keratotomy in epikeratophakia. Journal of Refractive Surgery. 1986;2:61-66.

37. Friedlander MH, Neumann AC, Durrie DS, Nordan LT. Consultations: problem case 2. Refract Corneal Surg. 1990;6:281-282.

38. Steinert R, Grene R. Postoperative management of epikeratoplasty. J Cataract Refract Surg. 1988;14:255-264.

39. McDonald M, Kaufman H, Aquavella J, et al. The nationwide study of epikeratophakia for aphakia in adults. Am J Ophthalmol. 1987;103:358-365.

40. Thompson K, Hanna K, Waring GO. Emerging technologies for refractive surgery: laser adjustable synthetic epikeratoplasty. Refract Corneal Surg. 1989;5:46-48.

41. Maxwell W. Myopic keratomileusis: initial results and myopic keratomileusis combined with other procedures. J Cataract Refract Surg. 1987;13:518-524.

42. Girard L, Eguez I, Esnaola N, Barnett L, Maghraby A. Effect of penetrating keratoplasty using grafts of various sizes on keratoconic myopia and astigmatism. J Cataract Refract Surg. 1988;14:541-547.

43. Baumgartner S, Binder PS. Refractive keratoplasty. Histopathology of clinical specimens. Ophthalmology. 1985;92:16061615.

44. Binder PS. Pathologic Findings in Cases of Refractive Corneal Surgery. Transactions of the New Orleans Academy of Ophthalmology. New York, NY: Raven Press; 1987.

45. Lavery GW, Lindstrom RL, Hofer LA, Doughman DJ. The surgical management of corneal astigmatism after penetrating keratoplasty. Ophthalmic Surg. 1985;16:165-169.

46. Maxwell W, Nordan L, Trapezoidal relaxing incision for post keratoplasty astigmatism. Ophthalmic Surg. 1986;17:88-90.

47. Krachmer J, Ching J. Relaxing incisions for postkeratoplasty astigmatism. Int Ophthalmol Clin. 1983;23:153-159.

48. Rapuano C, Cohen E, Brady S, et al. Indications for and outcomes of repeat penetrating keratoplasty. Am J Ophthalmol. 1990;109:689-695.

49. Binder PS. The triple procedure. Refractive results. 1985 update. Ophthalmology. 1986;93:1482-1488.

50. Binder PS. Intraocular lens implantation after penetrating keratoplasty. Refract Corneal Surg. 1989;5:224-230.

51. Friedlander M, Granet N. An unusual ease of an anterior and posterior chamber lens used in the same eye for refractive purposes. Journal of Refractive Surgery. 1987;3:170-172.

52. Goosey JD, Vila-Coro AA Epikeratophakia following rotational autokeratoplasty in a child. Cornea. 1987;6:140-143.

53. Maloney W, Sanders D, Pearcy D. Astigmatic keratotomy to correct preexisting astigmatism in cataract patients. J Cataract Refract Surg. 1990;16:297-304.

54. Thornton SP. Postcataract refractive surgery. Ophthalmic Practice. 1989;7:150-152.

55. Thornton S, Sanders D. Graded nonintersecting transverse incisions for correction of idiopathic astigmatism. J Cataract Refract Surg. 1987;13:27-31.

56. Fechner PU. Intraocular lenses for the correction of myopia in phakic eyes: short-term success and long-term caution. Refract Corneal Surg. 1990;6:242-244.

57. Colin J, Mimouni F, Robinet A, Conrad H, Mader P. The surgical treatment of high myopia: comparison of epikeratoplasty, keratomileusis and minus power anterior chamber lenses. Refract Corneal Surg. 1990;6:245-251.

58. Baikoff G, JoIy P Comparison of minus power anterior chamber intraocular lenses and myopic epikeratoplasty in phakic eyes. Refract Corneal Surg. 1990;6:252-260.

59. Binder PS, Barraquer J, Villaseñor R, Shaw E, Elander R. The Histopathology of Human Refractive Keratoplasty. International Congress of Ophthalmology, Acta XXTV. Philadelphia, Pa: JB Lippineott; 1982.

60. Binder PS. Refractive surgery: its current status and its future. CLAOJ. 1985;11:358-375.

Table 1

Complications Following Refractive Surgery

Table 2

Refractive Surgery Specimens Studied 1978 to 1991

Table 3

Outline of Theoretical and Actual Surgical Procedures Performed Following Refractive Surgical Procedures

Table 6

Case 3

Table 10

Case 8

10.3928/1081-597X-19920101-14

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