Corneal Refractive Surgery (Techniques and Technology) Ashok Garg, Dimitrii Dementiev, Ioannis G Pallikaris, Roberto Pinelli
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The Evolution of Lamellar Corneal ProceduresCHAPTER 1

Ioannis G Pallikaris
Theokliti G Papadaki
(Greece)
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INTRODUCTION
The roots of lamellar refractive corneal surgery lay in Bogota, Colombia and in the genius, persistent work of Professor Jose Ignacio Barraquer. Based on the fundamental principle that the cornea contributes two-third of the refracting power of the eye, as most light reflection occurs at the air/tear film interface, Barraquer attempted to alter the tear film/anterior cornea interface radius of curvature by adding or removing corneal tissue.1 Corneal lamellar procedures (Figure 1.1) were developed in an effort to preserve each layer of the cornea. The term keratomileusis, which is derived from the Greek roots keras (horn-like=cornea) and smileusis (carving), was introduced to describe lamellar techniques.2
 
KERATOMILEUSIS IN SITU
Keratomileusis in situ for myopia, was the first to develop in the late 1940s. The procedure involves raising a corneal cap and removing tissue from the residual stromal bed.
Barraquer's initial technique consisted of performing a free-hand lamellar dissection of the anterior half of the cornea using a Paufique knife or a keratome, to create a corneal cap. Subsequently, the refractive cut was attempted by removing stroma from the bed (keratomileusis in situ) with a second pass of the knife or keratome. When the cap was replaced, the anterior corneal curvature was flattened, thus, reducing the myopic refractive error.3
The many technical difficulties of keratomileusis in situ could not be overcome with the instrumentation available at that time, and the procedure had, therefore, to be temporarily abandoned.33
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FIGURE 1.1: Evolution of lamellar corneal procedures
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KERATOPHAKIA
Barraquer, however, would not abandon the efforts to perfect lamellar techniques. His ingenuity and persistence led to the development of keratophakia (KF), which was first introduced in 1961.4 KF involves steepening of the central corneal curvature by placing a disk of tissue under the lamellar cap. At that time, the added tissue was invariably an alloplastic stromal disk harvested from a donor cornea with the use of a microkeratome. The disk diameter and thickness varied, depending on the initial refractive error and the target correction. KF attracted the attention of the ophthalmic community as a possible solution in the treatment of aphakia after cataract extraction.5 With the advent of IOL technology, interest in KF subsided, since IOLs featured the more accurate refractive results without the technical difficulties of harvesting the donor tissue and performing the lamellar cut.
 
FREEZE MYOPIC KERATOMILEUSIS
In an effort to overcome the technical difficulties of the manual cut, Barraquer was the first to use the contact lens lathe to sculpture the frozen lamellar corneal cap, and so freeze keratomileusis was introduced.47 Theoretically, this new technique could be used to achieve either myopic or hyperopic corrections. However, Barraquer found myopic corrections more successful, thus, he focused his research on refining the freeze myopic keratomileusis (MKM) technique. Barraquer recognized that the cutting speed as well as the relation between IOP and the diameter of the resection, were factors directly affecting the quality and depth of the cut.3 His efforts for 5more predictable, reproducible and accurate cuts, led to the development of applanator lenses, suction rings of various diameters and various heights of microkeratome tracks.6 This work constituted the basis for future microkeratome evolution.
Although first reported results on freeze MKM were encouraging,3 the technique proved to have two major disadvantages:
  • The cryolathe was too expensive to obtain and too complex to maintain
  • The learning curve was too steep, involving high rate of complications such as irregular astigmatism or corneal scarring.7
At the same time, other techniques were introduced for the correction of refractive errors, such as epikeratophakia,5,813 incisional keratotomy1416 and IOL implantation.17,18
 
EPIKERATOPHAKIA (EPIKERATOPLASTY)
Kaufmann and Werblin introduced epikeratophakia or epikeratoplasty in 1979.8 In an effort to avoid the use of a cryolathe, the innovators attempted to use preprocessed refractive lenticles. A stromal disk was removed from a donor eye with the use of a microkeratome. The disk was frozen and lathed into a concave or convex lens. The lens was then lyophilized and stored for later use. Epikeratophakia was intended for use in the treatment of aphakia, myopia, hyperopia and keratoconus.1113 Its major advantages were simplicity and reversibility. Unfortunately, the initial reports showed that the technique was neither predictable nor safe.1822 Major problems 6related to the procedure were poor predictability and complications related to the re-epithelialization of the donor lenticle (persistent epithelial defects, epithelial ingrowth, melting, scarring). Furthermore, it was shown that upon removal of the epilenticle, there remained, occasionally, irreversible changes in the patient's initial refractive error.23 Several modifications were proposed in an effort to improve epikeratophakia.29,30 Burrato and Ferrari used the BKS system and Altmann used the excimer laser to shape epilenticles without freezing.31 However, as the difficulties could not be overcome, epikeratoplasty was withdrawn from the market and research turned once again towards keratomileusis techniques.
 
BARRAQUER-KRUMEICH-SWINGER (BKS) TECHNIQUE
By that time it was well understood that one of the major problems regarding freezing procedures was that they were often complicated with corneal haze and induced irregular astigmatism.2428 Inaccuracy of both epikeratoplasty and freeze MKM was in part attributed to the changes and variables introduced during the excessive processing of the epilenticle button or the corneal cap, respectively.32,33 Investigations in the direction of developing nonfreezing techniques led to the development of the Barraquer-Krumeich-Swinger (BKS) technique in 1985.34 This technique included an improved microkeratome (the BKS microkeratome), a set of dyes and a suction stand. The microkeratome was used to perform a total lamellar cap. The cap was then placed epithelial side down, on one of the suction dyes for the microkeratome to perform the 7second refractive cut at the stromal aspect of the cap. The dye was selected depending on the amount of the attempted correction of myopia or hyperopia. The sculptured lamellar disk was finally sutured back to the bed. Despite their technical difficulty, nonfreezing techniques proved to have a major advantage—the rapid and comfortable recovery of the patients. This was attributed to the preservation of fibroblasts and corneal epithelium. However, significant amounts of irregular astigmatism could not be avoided.35
In 1987, Leo Bores performed the first keratomileusis in situ in the US.2 Keratomileusis in situ with the use of manual microkeratomes, however, was reported as being not technically safe, precise or predictable and failed to be adopted by a large number of surgeons.36 Research began in the direction of developing new improved microkeratomes in an effort to improve the reproducibility and accuracy of the in situ technique.37
 
AUTOMATED LAMELLAR KERATOPLASTY (ALK)
The development of the automated geared microkeratome by Ruiz in the late 1980s introduced automated lamellar keratoplasty (ALK) in the field of lamellar refractive corneal surgery. The speed of the cut could be controlled by the foot pedal resulting in more even and consistent cuts. The keratome would also automatically reverse at the end of the procedure, without disturbing the lamellar cut. The second, refractive cut was subsequently performed on the bed. The depth of the second cap was adjusted by altering the height of the suction ring.8
ALK has been a breakthrough for lamellar surgery. Initially, the corneal cap was sutured back to the stromal bed, but very soon suturing was abandoned as unnecessary. The total operative time was reduced and the procedure could be safely performed under topical anesthesia. Recovery time improved. ALK was greatly popularized as many surgeons who found it difficult to use the manual microkeratomes adopted the new technique.
The first clinical trials on ALK revealed its advantages: (i) ease of use, (ii) rapid recovery and stability of refraction, and (iii) efficacy in the correction of high myopia. Major disadvantages, however, where the relative high rate for irregular astigmatism (2%) and the poor predictability of the procedure (within 2D).38 The latter was attributed to the imprecision of the depth obtained with the second resected disk. Research now focused on improving the accuracy of the second disk resection. It was at that time when we thought to combine the precision of photorefractive keratectomy (PRK) with the technique of ALK.
Trokel et al suggested PRK in 1983.39 As the use of 193 nm excimer laser in refractive surgery generated, it was revealed that for myopias greater than 6D, PRK resulted in significant central corneal haze, regression of refractive effect and poor predictability.40
 
LASER IN SITU KERATOMILEUSIS (LASIK)
Laser in situ keratomileusis (LASIK) was introduced, designed and developed at the University of Crete and 9the Vardinoyannion Eye Institute of Crete (VEIC) in 1988.41 The term laser in situ keratomileusis (LASIK) was introduced to describe a combination of lamellar refractive corneal surgery and excimer laser photoablation of the cornea under a hinged corneal flap. The idea of raising a corneal flap and removing central tissue from the bed was first described by Pureskin in 1966.42 He attempted to do the cut manually and cut out the in situ part with a trephine.
In LASIK the automated microkeratome is used to create a corneal flap. The refractive second cut is then substituted by the excimer laser submicron accuracy of stromal tissue removal. The initial hypothesis was that a flap would assure better fitting of tissues after removing the intrastromal tissue with laser, and would not affect the anatomic relations of corneal layers mainly by two ways:
  1. Preservation of Bowman's layer.
  2. Integrity of the nervous net at the superficial part of the cornea, as the latter follows at a great length its route through the base of the flap.
Other important factors were reduction of maneuvers and total time required for the operation.
The first animal studies to determine wound healing reactions after LASIK, began in 1987, using a Lamda Physik excimer laser and a specially designed microkeratome that was designed to produce a 150-micron flap instead of a total cap. It was suggested that stromal ablation could potentially avoid the regression of effect and stromal haze related to PRK, as the ablated area is hidden from the normal healing process of the eye that takes place at the epithelium/stroma interface.43,48
The first papers on LASIK were presented at the Seventh European Congress of the ESCRS in Zurich in 10August 1989 and published in 1990.43 The first LASIK on a blind human eye was performed in June 1989, as a part of an unofficial blind eye protocol.
 
EXCIMER LASER INTRASTROMAL KERATOMILEUSIS
Later on, in 1992, Lucio Buratto reported on excimer laser intrastromal keratomileusis, a technique where photoablation was performed under a corneal cap. First results on a large series of human eyes proved that this technique was efficient yet not safe. Complication rates were comparable to that of MKM.44
Stephen Slade and Brint were the first to perform LASIK in the US in 1992. During the 1993 American Academy of Ophthalmology Meeting, George Waring gave LASIK the temporary names “flap and zap” in order to emphasize the alacrity of the procedure. The major advantages of the procedure, appreciated by patients and surgeons alike include:
  • Minimal postoperative discomfort
  • Early recovery of visual function
  • Lack of adverse healing phenomena such as haze formation
  • Increased range of efficacy over PRK in myopia, hyperopia and astigmatism.
To date, there have been published several articles concerning healing of partially sighted eyes,45,46 results on partially sighted eyes,47 a comparative study between LASIK and PRK in partially sighted eyes51 and series of normal sighted eyes with varying follow-up.49
Several clinical studies on LASIK since 1995, reveal that refractive results are far from optimum. Accuracy and 11predictability proves greater with lower diopters of myopia, while certain studies report a high rate of intraoperative complications, comparable to that of other lamellar techniques.5072
LASIK is the most recent step in the evolution of lamellar corneal techniques, initiated by Barraquer 50 years ago. Reports to date are encouraging, although longer follow-up data are expected. Meanwhile, continuous research in the direction of improving microkeratomes and readjusting laser algorithms will hopefully improve the predictability, safety and stability of the procedure.
Reviewing the history of lamellar refractive surgery is essential for better understanding and further refining the currently used techniques. Continuing evolution in all fields of refractive surgery is the only way to approach the ultimate goal, which should be to offer our patients a better vision, both Qualitatively and Quantitatively.
REFERENCES
  1. Barraquer JI. Oueratoplastia refractiva. Estudios Inform 1949;10:2–21.
  1. Bores L. Lamellar refractive surgery. In Bores L (Ed): Refractive Eye Surgery. Blackwell Scientific Publications:  Boston  1993;324–92.
  1. Barraquer JI. Keratomileusis. Int Surg 1967;48:103–17.
  1. Barraquer JI. Method for cutting lamellar grafts in frozen corneas–new orientations for refractive surgery. Arch Soc Am Ophthalmol 1958;1:237.
  1. Kaufmann HE. The correction of aphakia. Am J Ophthalmol 1980;89:1–10.
  1. Barraquer JI. Results of myopic keratomileusis. J Refract Surg 1987;3:98–101.

  1. 12 Littman H. Optic of Barraquer's keratomileusis. Arch Oftal Optom 1966;6:1.
  1. Werblin TP, Klyce SD. Epikeratophakia–the correction of aphakia: I–lathing of corneal tissue. Curr Eye Res 1981; 1:591–97.
  1. Barraquer JI. Modification of refraction by means of intracorneal inclusions. Int Ophthalmol Clin 1966;6:53–78.
  1. Baumgartner SD, Binder PS, Deg JK, et al. Epikeratophakia–clinical and histopathologic evaluation in non-human primates. Invst Ophthalmol Vis Sci 1983;24:148.
  1. Werblin TP, Kaufmann HE, Friedlander MH, et al. A prospective study of the use of hyperopic epikeratophakia grafts for the correction of aphakia in adults. Ophthalmology 1981;88:1137–40.
  1. Kaufmann HE, Werblin TP. Epikeratophakia–a form of lamellar keratoplasty for the treatment of keratoconus. Am J Ophthalmol 1982;93:342–47.
  1. Werblin TP, Blaydes JE, Kaufmann HE. Epikeratophakia–the correction of astigmatism: Preliminary experimental results. CLAOJ 1983;9:61–63.
  1. Bores LD, Myers W, Cowden J. Radial keratotomy–an analysis of the American experience. Ann Ophthalmol 1981;13:941–48.
  1. Arrowsmith PN, Sanders DR, Marks RG. Visual, refractive and keratometric results of radial keratotomy. Arch Ophthalmol 1983;101:873–81.
  1. Deitz MR, Sanders DR, Marks RG. Radial keratotomy–an overview of the Kansas city study. Ophthalmology 1984;91:467–78.
  1. Shearing SP. Posterior chamber lens implantation. Int Ophthalmol Clin 1982;22:135–53.
  1. McDonald MB, Kaufmann HE, Aquavella JV, et al. The nationwide study of epikeratophakia for aphakia in adults. Am J Ophthalmol 1897;103:350–65.
  1. McDonald MB, Kaufmann HE, Aquavella JV, et al. The nationwide study of epikeratophakia for myopia in adults. Am J Ophthalmol 1897;103:375–83.
  1. Reidy JJ, McDonald MB, Klyce SD. The corneal topography of epikeratophakia. Refract Corn Surg 1990;6:26–31.

  1. 13 Wilson DR, Keeney AH. Corrective measures for myopia. Surv Ophthalmol 1990;34:294–304.
  1. Goosey JD, Prager TC, Goosey CB, et al. Stability of refraction during two years after myopic epikeratoplasty. Refract Corneal Surg 1990;6:4–8.
  1. Rozakis GW, Slade SG, et al. Refractive Lamellar Keratoplasty Slack: Thorofare 1994.
  1. Swinger CA, Barker BA. Prospective evaluation of myopic keratomileusis. Ophthalmology 1984;91:785–92.
  1. Nordan LT, Fallor MK. Myopic keratomileusis–74 consecutive non-amblyopic cases with one year follow-up. J Refr Surg 1986;2:124–28.
  1. Maquire LJ, Klyce SD, Sawelson H, et al. Visual distortion after myopic keratomileusis–computer analysis of keratoscope photographs. Ophthalmic Surg 1987;18:352–56.
  1. Nordan LT. Keratomileusis. Int Ophthalmol Clin 1991;31:7–12.
  1. Barraquer C, Guitierrez A, Espinoza A. Myopic keratomileusis–short-term results. Refract Corneal Surg 1989; 5:307–13.
  1. Slade SG, Strauss GH. Use of tissue adhesive (Tisseel) in epikeratophakia. Invest Ophthalmol Vis Sci 1990;31:30.
  1. Goosey JD, Prager TC, Marvelli TL, et al. Epikeratophakia without annular keratectomy. Ann Ophthalmol 1987;19:388–91.
  1. Altmann J, Grabner C, et al. Corneal lathing using the excimer laser and a computer-controlled positioning system: part I–lathing of epikeratoplasty lenticules. Refract Corneal Surg 1991;7:377–84.
  1. Friedlander MH, Rich LF, Werblin TP, et al. Keratophakia using preserved lenticles. Ophthalmology 1991;87:687–92.
  1. Zavala EY, Krumeich J, Binder PS. Laboratory evaluation of freeze vs no-freeze lamellar refractive keratoplasty. Arch Ophthalmol 1991;105:1125–28.
  1. Swinger CA, Krumeich J, Cassiday D. Planar lamellar refractive keratoplasty. I Refract Surg 1986;2:17–24.
  1. Colin J, Mimouni F, Robinet A. The surgical treatment of high myopia–comparison of epikeratoplasty, keratomileusis 14and minus power anterior chamber lenses. Refract Corneal Surg 1990;6:245–51.
  1. Arenas-Archila E, Sanchez-Thorin JC, et al. Myopic keratomileusis in situ–a preliminary report. J Cataract Refract Surg 1991;17:424–35.
  1. Hofmann RF, Bechara SJ. An independent evaluation of second generation suction microkeratomes. Refract Corneal Surg 1992;8:348–54.
  1. Slade SG, Updegraff SA. Complications of automated lamellar keratectomy (comment). Arch Ophthalmol 1995;113 (9):1092–93.
  1. Trokel S, Srinivasan R, Braren B. Excimer laser surgery of the cornea. Am J Ophthalmol 1995;94:125.
  1. Seiler T, McDonnell PJ. Excimer laser photorefractive keratectomy. Surv Ophthalmol 1995;40(2):89–118.
  1. Pallikaris I, Papatzanaki M, Stathi EZ, et al. Laser in situ keratomileusis. Laser Surg Med 1990;10:463–68.
  1. Pureskin N. Weakening ocular refraction by means of partial stromectomy of the cornea under experimental conditions. Vestn Oftalmol 1967;8:1–7.
  1. Pallikaris I, Papatzanaki ME, Georgiadis A, et al. A comparative study of neural regeneration following corneal wounds induced by argon fluoride excimer laser and mechanical methods. Lasers Light Ophthalmol 1990;3:89–95.
  1. Buratto L, Ferrari M, Rama P. Excimer laser intrastromal keratomileusis. Am J Ophthalmol 1992;113:291–95.
  1. Pallikaris IG, Papatzanaki ME, Siganos DS, et al. A corneal flap technique for laser in situ keratomileusis. Arch Ophthalmol 1991;109(12):1699–1702.
  1. Pallikaris IG, Papatzanaki ME, Siganos DS, et al. Tecnica de colajo corneal para la queratomileusis in situ mediane laser–estudios en humanos. Arch Ophthalmol (Ed Esp) 1992;3(3):127–30.
  1. Siganos DS, Pallikaris IG. Laser in situ keratomileusis in partially sighted eyes. Invest Ophthalmol Vis Sci 1993;34(4):800.

  1. 15 Pallikaris IG, Siganos DS. Excimer laser in situ keratomileusis and photorefractive keratectomy for the correction of high myopia. J Refract Corneal Surg 1994;10(15):498–510.
  1. Pallikaris IG, Siganos DS. Corneal flap technique for excimer laser in situ keratomileusis to correct moderate and high myopia–two year follow-up (best papers of sessions). ASCRS Symposium on Cataract, IOL and Refractive Surgery  1994;9–17.
  1. Bas AM, Onnis R. Excimer laser in situ keratomileusis for myopia. J Refract Surg 1995;11(suppl): 229–33.
  1. Fiander DC, Tayfour F. Excimer laser in situ keratomileusis in 124 myopic eyes. J Refract Surg 1995;11(suppl): 234–38.
  1. Knorz MC, Liermann A, Steiner H. Laser in situ keratomileusis to correct myopia of −6 to −29 diopters. J Refract Surg 1996;12:575–84.
  1. Salah T, Waring III GO, El Meghraby A, et al. Excimer Laser in situ keratomileusis under a corneal flap for myopia of 2 to 20 diopters. Am J Ophthalmol 1996; 121:143–55.
  1. Guell JL, Muller A. Laser in situ keratomileusis (LASIK) for myopia ranging from −7 to −18 Diopters. J Refract Surg 1996;12:222–28.
  1. Perez-Santonja JJ, Bellot Claramonte P, Ismail MM, et al. Laser in situ keratomileusis to correct high myopia. J Cat Refract Surg 1997;23:372–85.
  1. El Danasoury MA, Waring GO, El Maghraby A, et al. Excimer laser in situ keratomileusis to correct compound myopic astigmatism. J Refract Surg 1997;13:511–21.
  1. Marinho A, Pinto MV, Pinto R, et al. LASIK for high myopia–1 year experience. Ophthal Surg Lasers 1997;27: S517–20.
  1. Casebeer JC, Kezirian GM. Outcomes of spherocylinder treatments in the comprehensive refractive surgery LASIK study. Semin Ophthalmol 1998;13(2):71–78.
  1. Argento CJ, Cosentino MJ. Laser in situ keratomileusis for hyperopia. J Cataract Refract Surg 1998;24(8):1050–58.
  1. Carr JD, Stulting RD, Sano Y, et al. Prospective comparison of single-zone and multizone laser in situ keratomileusis for 16the correction of low myopia. Ophthalmology 1998; 105(8):1504–11.
  1. Farah SG, Azar DT, Gurdal C, et al. Laser in situ keratomileusis–literature review of a developing technique. J Cataract Refract Surg 1998;24(7):989–1006.
  1. Knorz MC, Wiesinger B, Liermann A, et al. Laser in situ keratomileusis for moderate and high myopia and myopic astigmatism. Ophthalmology 1998;105(5):932–40.
  1. Davidorf JM, Zaldivar R, Oscherow S. Results and complications of laser in situ keratomileusis by experienced surgeons. J Refract Surg 1998;14(2):114–22.
  1. Ibrahim O. Laser in situ keratomileusis for hyperopia and hyperopic astigmatism. J Refract Surg 1998;14(2 suppl): 179–82.
  1. Lavery F. Laser in situ keratomileusis for myopia. J Refract Surg 1998;14(2 suppl):177–78.
  1. Chayet AS, Magallanes R, Montes M, et al. Laser in situ keratomileusis for simple myopic, mixed and simple hyperopic astigmatism. J Refract Surg 1998;14(2 suppl): 175–76.
  1. Maldonado-Bas A, Onnis R. Results of laser in situ keratomileusis in different degrees of myopia. Ophthalmology 1998;105(4):606–11.
  1. Goker S, Er H, Kahvecioglu C. Laser in situ keratomileusis to correct hyperopia from +4.25 to +8.00 diopters. J Refract Surg 1998;14(1):26–30.
  1. Zaldivar R, Davidorf JM, Oscherow S. Laser in situ keratomileusis for myopia from −5.5 to −11.50 diopters with astigmatism. J Refract Surg 1998;14(1):19–25.
  1. Salchow DJ, Zirm ME, Stieldorf C, et al. Laser in situ keratomileusis for myopia and myopic astigmatism. J Cataract Refract Surg 1998;24(2):175–82.
  1. Lindstrom RL, Hardten DR, Chu YR. Laser in situ keratomileusis (LASIK) for the treatment of low moderate, and high myopia. Trans Am Ophthalmol Soc 1998;95:285–96.
  1. Waring GO 3rd, Carr JD, Stulting RD, et al. Prospective, randomized comparison of simultaneous and sequential bilateral LASIK for the correction of myopia. Trans Am Ophthalmol Soc 1997;95:271–84.