From London Vision Clinic, London, United Kingdom (Reinstein, Archer, Gobbe); the Department of Ophthalmology, Columbia University Medical Center, New York, New York (Reinstein); and Centre Hospitalier National d’Ophtalmologie, Paris, France (Reinstein).
The authors have no financial interest in the materials presented herein.
The authors thank the following for their invaluable contributions of photos, video, and other materials: Carmen Barraquer, MD; Jose Ignacio Barraquer Moner, MD; Lucio Buratto, MD; Jose L. Guell, MD; Khalil Hanna, MD; Jairo E. Hoyos, MD; Jörg H. Krumeich, MD; John Marshall, PhD; Marguerite B. McDonald, MD; Ioannis G. Pallikaris, MD, PhD; Yaron S. Rabinowitz, MD; Aleksander Razhev, MD; Luis A. Ruiz, MD; Theo Seiler, MD, PhD; Casimir A. Swinger, MD; John Taboada, PhD; Stephen L. Trokel, MD; Richard C. Troutman, MD; Alfred Vogel, PhD; George O. Waring III, MD; James J. Wynne, PhD; the Medical University of Lublin, Lublin, Poland; and the International Society of Refractive Surgery.
Study concept and design (D.Z.R., T.J.A., M.G.); data collection (D.Z.R., T.J.A., M.G.); analysis and interpretation of data (D.Z.R., T.J.A., M.G.); drafting of the manuscript (D.Z.R., T.J.A., M.G.); critical revision of the manuscript (D.Z.R.)
Correspondence: Dan Z. Reinstein, MD, MA(Cantab), FRCSC, FRCOphth, London Vision Clinic, 138 Harley St, London W1G 7LA, United Kingdom. Tel: 44 207 224 1005; Fax: 44 207 224 1055; E-mail firstname.lastname@example.org
Laser in situ keratomileusis (LASIK) has become the single most common elective operation with over 35 million procedures performed worldwide by 2010.1 It has evolved into a 10-minute process that can correct 96% of all refractive errors with minimal discomfort, a recovery time of a few hours, and dramatic visual results overnight. It is the confluence of numerous brilliant ideas and bioengineering accomplishments that have led to what is now one of the most miraculous procedures in the history of medicine.
The concept that refractive error could be corrected by sculpting corneal stromal tissue to change corneal curvature was the brainchild of Jose Ignacio Barraquer Moner in 1948.2–4 Barraquer developed a procedure he coined “keratomileusis,”5 which involved ressecting a disc of anterior corneal tissue that was then frozen in liquid nitrogen, placed on a modified watchmaker’s lathe (Fig 1), and milled to change corneal curvature (Fig 2). The word “keratomileusis” literally means “sculpting” of the “cornea.”
Figure 1. Jose I. Barraquer Moner using his first cryolathe to mill the underside of a ressected disc of anterior corneal tissue. This original lathe was a modified watchmaker’s lathe. (Image courtesy of Carmen Barraquer, MD.)
Figure 2. Close-up of the corneal milling showing tissue being removed from the underside of the frozen ressected disc. (Image courtesy of Carmen Barraquer, MD.)
The resection was achieved using a manually driven microkeratome that he designed specifically for this purpose based on a carpenter’s plane (Fig 3). Barraquer then used trigonometric calculations to derive the volume of tissue removal required for a particular refractive error correction. In his 1964 thesis on the “Law of Thicknesses”6 (Fig 4), he described that “the cornea flattens when tissue is removed from the center and steepens when tissue is removed from the periphery.”
Figure 3. Photograph (above) and technical diagram (below) of the first manually driven microkeratome developed by Barraquer for corneal disc resection in keratomileusis. (Image courtesy of Carmen Barraquer, MD.)
Figure 4. Trigonometric diagram that formed the basis of the calculations for Barraquer’s Law of Thicknesses on which keratomileusis and all future corneal tissue removal/ablation procedures were based. The diagrams demonstrate the tissue that needs to be removed in a myopic (left) and hyperopic (right) correction. (Reprinted with permission from Barraquer JI. Queratomileusis y Queratofaquia. Bogota, Colombia: Instituto Barraquer de América; 1980:125. Copyright © 1980.)
His earliest patients were treated in the early 1960s at the Clinica de Marly in Bogota, Colombia, where he had to leave the patient on the operating table after ressecting the corneal disc while he hurried 3 km across town to where he had set up the lathing workshop in his home. After reshaping the corneal disc with his cryolathe, he would drive back to the hospital to suture the thawed and reshaped corneal disc back onto the patient’s eye (Carmen Barraquer, MD, personal communication, May 11, 2010). During the process of developing the keratomileusis procedure, he also invented a number of instruments and techniques to make his ideas a reality. His inventions included the torque anti-torque suture, the operating microscope, and many other microsurgical instruments commonly used in ophthalmic surgery today.
Around that time others were experimenting with Barraquer’s ideas. In Poland, Krwawicz7,8 published a paper in 1964 describing a series of three highly myopic eyes in which he had performed a “stromectomy.” He manually made two stromal cuts at different depths with a flat knife and removed the thin lamella of intervening stroma.
In Russia, Pureskin9 described in 1967 the concept of an incomplete anterior corneal resection to leave a naturally hinged flap, after which a stromal disc was removed by trephination (Fig 5). He reported a series of 71 rabbit eyes and described the power change achieved for discs with different diameters.
Figure 5. Diagram (top) and intraoperative photograph (bottom) of Pureskin’s technique of creating a hinged flap followed by trephination of a stromal disc. (Reprinted with permission from Pureskin NP. Weakening ocular refraction by means of partial stromectomy of cornea under experimental conditions [Russian]. Vestn Oftalmol. 1967;80(1):19–24. Copyright © 1967. Izdatelstvo Meditsina.)
Several thousand keratomileusis procedures were performed at the Instituto Barraquer de America in the 1970s and early to mid 1980s and surgeons from around the world came to learn this difficult but miraculous technique.
Two of Barraquer’s disciples, Krumeich and Swinger, worked on a refinement of the technique to perform keratomileusis without freezing, referred to as the Barraquer-Krumeich-Swinger (BKS) technique, which was published in 1986.10,11 This BKS non-freeze technique involved placing the ressected disc epithelial side down onto a curved suction die or mold where a second pass of the microkeratome removed tissue from the exposed posterior stromal surface according to the shape of the die (Fig 6). The BKS technique aimed to reduce surgical trauma to the tissues and improve visual recovery time.
Figure 6. Diagrams (above) and photographs (below) of a myopic (left) and hyperopic (right) suction die used in the Barraquer-Krumeich-Swinger non-freeze technique. The ressected corneal disc was placed epithelial side down onto the die and a second pass of the microkeratome removed the required stromal tissue. For myopic corrections, the shape of the die exposed central stroma, whereas the shape of the die exposed peripheral stroma for hyperopic corrections. A set of suction dies with different curvatures were available to treat a wide range of different refractions. (Image courtesy of Jörg H. Krumeich, MD.)
In Situ Keratomileusis
Around the same time, another non-freeze technique called in situ keratomileusis12 was developed. The procedure was first performed by Ruiz, who having completed his residency at the Barraquer Institute, was performing up to 20 keratomileusis procedures a day. Ruiz was interrupted in his flow by a corneal disc resection that was found to be too thin for the required stromal tissue removal. With the patient on the table, he came up with the idea of passing the microkeratome a second time using a different suction ring with the height adjusted to resect the required lenticule directly from the stromal bed (Luis Ruiz, MD, personal communication, April 13, 2010). This was called in situ keratomileusis (Fig 7).
Figure 7. Intraoperative photograph of the stromal bed after two passes of the microkeratome. The first pass created the corneal disc resection while the second pass removed stromal tissue from the stromal bed in a smaller diameter to achieve the refractive correction. The resected corneal disc was then sutured back onto the eye. The calipers in the photograph show the diameter of the second pass, and the larger diameter of the first pass can also be seen. (Image courtesy of Jairo E. Hoyos, MD.)
Automated Lamellar Keratoplasty
Ruiz was responsible for designing a gear system to automate the passage of the microkeratome head (Luis Ruiz, personal communication, April 13, 2010). This eased the technical challenges of using a manual microkeratome, as the head could be passed with a constant and reproducible speed, thereby avoiding irregular resections and improving the accuracy. The procedure became known as automated lamellar keratoplasty (ALK). Automated lamellar keratoplasty was further refined by replacing the disc without a suture and adhesion was aided by drying, after which the eye was patched overnight until the epithelium sealed the disc into place (Luis Ruiz, MD, personal communication, April 13, 2010).
In 1989, Ruiz presented a paper demonstrating how a flap could be produced by stopping the microkeratome before the end of the pass.13 The flap would then be tucked under the second microkeratome ring applied for the stromal resection thus leaving a hinge to simplify the replacement of the cap and reduce cap-related complications.
In the early 1990s, in situ keratomileusis was combined with the emerging technology of excimer lasers for corneal tissue ablation to finally become LASIK as we know it today.14 But the excimer laser has a history of its own starting in 1900. After Max Planck had described the quantum theory,15 Albert Einstein predicted that the energy released by an electron moving from an outer orbital to a lower energy inner orbital could be initiated by an external source, which he called stimulated emission.16
It was not until 1952 that Einstein’s theory was made a reality when microwaves were used as the external source to produce Microwave Amplification of Stimulated Emission of Radiation (MASER). The MASER was pioneered by Townes and Schawlow17 (Bell Laboratories, Murray Hill, New Jersey) and simultaneously by Basov and Prokhorov18 (Lebedev Physical Institute, Moscow, Russia). Later, the microwave was replaced by light, and MASER became LASER (Light Amplification of Stimulated Emission of Radiation), as first defined (in his lab notebook) by Gordon Gould in 1957.
The breakthrough ideas were the use of optical pumping to initiate the process and amplification of the emission by using parallel mirrors, one of which was semi-reflective, to partially reflect photons back and forth through the active medium.
In 1970, the term excimer laser was introduced to describe a laser built by Basov using a xenon dimer gas, the name excimer coming from an abbreviation of “excited dimer.” The argon-fluoride excimer laser was developed in 1976.19,20
It was not until 1981 when an argon-fluoride excimer laser (193 nm) was fired on organic tissue when Srinivasan, Wynne, and Blum, who were researchers at IBM, made an incision in the leftover cartilage of a turkey from Thanksgiving dinner and found no evidence of damage to the surrounding tissue unlike the charring seen around an incision made with a solid-state laser with a wavelength of 532 nm (James J. Wynne, PhD, personal communication, December 9, 2011) (Fig 8), which they presented at the Conference on Lasers and Electro-Optics in May 1983.21,22 They demonstrated that complex patterns could be made at a micronic level with each pulse removing a fraction of a micron. This research was an outgrowth of excimer lasers being used for direct photoetching of polymers, with potential application to IBM’s microchip packaging technology.
Figure 8. Photographs of incisions into turkey cartilage made by a solid-state 532-nm laser (left incision) and an argon-fluoride 193-nm excimer laser (right incision). The charring can be seen with the solid-state laser, whereas the incision appears clean with no damage to the surrounding tissue with the excimer laser. (Image courtesy of James J. Wynne, PhD; Rangaswamy Srinivasan; and Samuel Blum.)
At the same time, Taboada also found no thermal damage to the remaining tissue after a 248-nm excimer laser pulse on corneal epithelium.23 Thus, it was established that excimer laser–tissue interaction was effectively non-thermal, but rather direct splitting of molecular bonds with minimal adjacent heating. This process was coined “photoablation”24 (Fig 9).
Figure 9. Photograph of the plume immediately after an excimer laser pulse. (Reprinted with permission from Noack J, Tönnies R, Hohla K, Birngruber R, Vogel A. Influence of ablation plume dynamics on the formation of central islands in excimer laser PRK. Ophthalmology. 1997;104(5):823–830. Copyright © 1997. Elsevier.)
Trokel had been evaluating the possibility of using different lasers (such as carbon dioxide and Nd:YAG lasers) for radial keratotomy incisions, but none that he had tried were suitable for corneal application. Trokel first learned of excimer lasers after reading Taboada’s paper, which encouraged him to investigate the potential of corneal applications for the excimer laser (Stephen L. Trokel, MD, personal communication, August 18, 2010; John Taboada, PhD, personal communication, August 16, 2010). Trokel was introduced to Srinivasan at IBM, who agreed to work with him to investigate the potential of using an excimer laser to improve the accuracy of radial keratotomy incisions.25,26 Marshall began working with Trokel to study the ultrastructural aspects of corneal photoablation.27 They compared the quality of the wounds made by an excimer laser at 193 nm with one at 248 nm as well as wounds made by steel and diamond blades (Fig 10). The quality of the wounds was best with 193 nm.28 This finding was in agreement with similar studies by other groups29–32 at that time.
Figure 10. Light micrographs of rabbit corneas incised by A) an argon fluoride excimer laser (193 nm), B) a krypton fluoride excimer laser (248 nm), C) a Micra diamond knife, and D) a Sharpoint steel blade. The wound quality is best with the argon fluoride excimer laser. (Reprinted with permission from Marshall J, Trokel S, Rothery S, Krueger RR. A comparative study of corneal incisions induced by diamond and steel knives and two ultraviolet radiations from an excimer laser. Br J Ophthalmol. 1986;70(7):482–501. Copyright © 1986. BMJ Publishing Group Ltd.)
The wound quality suggested to Marshall that large area ablation could be performed in the central cornea, rather than just for peripheral linear incisions (John Marshall, PhD, personal communication, May 30, 2010). Marshall described this in 1986 as photorefractive keratectomy (PRK).33 For PRK to become a feasible procedure in human eyes, the following criteria needed to be satisfied. First, the depth of tissue removal required for a given refraction change must be known. Munnerlyn proposed an algorithm adapted from Barraquer’s earlier formulae to calculate the ablation profile as a function of refractive error and optical zone diameter.34 Second, the quality and clarity of the ablated surface must be preserved. Earlier studies in rabbit corneas demonstrated only limited haze after a large area ablation.33 Myopic ablation on a donor eye also showed that the ablated surface was clean and smooth.35 Third, the wound-healing process must not result in scarring. It was already known that no scarring occurred after radial incisions.36,37 Marshall et al38 then demonstrated no changes in corneal transparency 8 months after PRK in 12 monkey corneas, and McDonald et al39 reported stable dioptric change in a primate cornea with good healing and long-term corneal clarity up to 1 year after PRK.
In 1985, Seiler et al36 performed the first large area ablation in a live patient to remove corneal dystrophy scarring, having previously performed T-incisions earlier that year with an excimer laser to correct for astigmatism. With the increasing interest in the possibility of performing refractive correction with an excimer laser, the first international workshop on laser corneal surgery was held in Berlin in 1986.
This led to PRK being performed in humans. In early 1988, McDonald performed the first PRK on a sighted eye due for enucleation, while at around the same time L’Esperance et al40 and Seiler et al41 also began performing PRK in blind eyes.
Central ablation of the cornea was performed using different methods. L’Esperance suggested small scanning spot excimer lasers, which could be controlled to ablate in specific patterns.42 Marshall proposed using a broad-beam laser and a moving iris diaphragm to shape the area to be ablated. For a myopic correction, initially the aperture was sequentially reduced in diameter to create steps on the corneal surface. The number of steps was gradually increased to improve the smoothness of the curved surface (Fig 11).43 Hanna et al44 used a rotating-slit laser delivery system; the shape of the slit was determined mathematically to obtain a parabolic ablation profile that resulted from the slit rotation.
Figure 11. Image of a myopic ablation performed using a broad-beam laser and a moving iris diaphragm. The diameter of the iris diaphragm was gradually reduced, which created a series of small steps. The number of steps was increased to better approximate a curved surface. (Image courtesy of John Marshall, PhD.)
Larger clinical trials followed with commercial excimer lasers given the encouraging results from the first cases. In 1991, McDonald and Kaufman et al45 reported that myopic PRK treatment with the VISX 20/20 (VISX Inc, Santa Clara, California) system was safe. In the same year, Lindstrom and Sher et al46–48 demonstrated the safety and efficacy of the Taunton Technologies (Monroe, Connecticut) model LV 2000 excimer laser for myopic PRK. Also at that time, the Marshall49,50 and Seiler51 groups published outcomes using the Summit Technology Eximed UV200 excimer laser (Summit Technologies, Waltham, Massachusetts). During the same year, Dausch and Schroeder52 presented results in high myopes with the Aesculap-Meditec (Jena, Germany) excimer laser and later, in 1993, presented the first hyperopic ablation profiles.
At this point, the excimer laser story joins the keratomileusis story to become laser in situ keratomileusis, or LASIK. The idea of using an excimer laser to ablate tissue under a flap was springing up in various parts of the world. In 1988, Razhev et al53–55 in Novosibirsk, USSR began using a 5-mm trephine to produce a central 100-μm deep circular keratotomy and then a scalpel to create a lamellar hinged flap (Aleksander Razhev, personal communication, August 23, 2010) (Fig 12).56 They then used an excimer laser to ablate the stromal bed before replacing the lamellar flap in four myopic and five hyperopic eyes. They presented their results with up to 2-year follow-up in September 1990 at Columbia University, New York.55
Figure 12. Intraoperative photograph during the first LASIK procedure performed by Razhev in 1988. The hinged flap can be seen to have been lifted and the excimer laser ablation can be visualised by the blue area on the stromal bed. (Image courtesy of Aleksander Razhev, MD.)
At around the same time, Buratto was performing classical keratomileusis,57 but in October 1989 he used an excimer laser for ablation on the underside of the cap (instead of a lathe or microkeratome) and published the results of his first 30 high myopic eyes with few complications and 1-year follow-up in 1992. In December 1989, Buratto had a case where the cap was too thin for the required tissue removal, much like Ruiz previously with ALK, and so decided instead to perform the excimer laser ablation directly on the stromal bed before replacing the cap (Lucio Buratto, MD, personal communication, July 1, 2010).
Pallikaris also produced a hinged flap using a microkeratome he had designed for rabbit studies and performed the ablation with an excimer laser on the exposed bed followed by replacement of the flap without sutures. The term “LASIK” was first used to describe this procedure in his 1990 paper.14,58 Pallikaris treated his first patients in October 1990 (Ioannis G. Pallikaris, MD, PhD, personal communication, July 1, 2010) and published his results on 10 high myopic eyes with 1-year-follow-up in 1994.59
It is this technique that gave birth to what is now the most commonly elective performed surgical procedure in the world1 and realized the dreams of Jose Ignacio Barraquer Moner 40 years in the making.
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