Refractive Surgery Amar Agarwal, Athiya Agarwal, Soosan Jacob
INDEX
×
Chapter Notes

Save Clear

SECTION ONE
1Basics, Instrumentation and Preoperative Assessment2

The History of Refractive Surgery1

Ioannis Pallikaris
 
INTRODUCTION
Based on the letter written by a prominent Roman, there were no instruments to improve vision at the time of the ancient Egyptians, Greeks or Romans. The letter is dated about 100 B.C. in which the Roman complains that he can no longer read for himself, instead he has to rely on his slaves. Lenses made of polished crystal did exist, but were used as “burning glasses” to erase writing from wax tablets; physicians at that time used burning glasses to cauterize wounds according to Pliny.
Around 1000 A.D. the reading stone, a segment of a glass sphere that could be laid against reading material to magnify the letters was first developed. The Venetians developed the first reading stones held in a frame in front of the eyes instead of directly on the reading material. However, it took over 350 years to develop a practical means to keep them on the face. Ribbons and strings were tied about the head for several hundred more years, until a London based optician named Edward Scarlett perfected the use of rigid sidepieces that rested atop the ears in 1730. These spectacles cost as much as $200 in the early 1700's. Benjamin Franklin is credited with creation of the bifocal in the 1780's by cutting two lenses in half and placing one above the other. As glass-making improved, so did the lenses and improvements in frame-making and materials resulted in several styles to choose from. But even at the turn of the 20th century, glass fitting was largely trial and error with the patient responsible for determining the correct lens, often in a rather casual manner.
As early as 1845, Sir John Herschel suggested the idea for contact lenses, but he evidently did nothing about it. The term contact lens originated with Dr. A. Eugen Fick, a Swiss physician, who published the results of experiments with contact lenses in 1887. Early contacts were created by blowing glass in different-sized bubbles and cutting them in half, polishing the edges and placing them in the eyes. Several doctors and optical firms in Europe cooperated in creating practical contact lenses over the decades around the turn of the 20th century. By the early 1940's a variety of materials were available: blown glass, ground glass, molded glass, plastic and glass and all plastics. All of these lenses were large and uncomfortable and couldn't be worn for long. By 1964 over 6 million people in the United States were wearing contact lenses, 65 percent of them were women.
The first experimental study about refractive surgery was performed by Lendeer Jans Lans, an ophthalmology teacher in Holland. In 1896 he published a theoretic work proposing penetrating corneal cuts to correct astigmatism. In 1930 the Japanese ophthalmologist Sato made the first practical attempt to perform such surgery in military pilots. He practiced radial cuts in the cornea to correct effects by up to 6 diopters. This approach proved disasterous 4as the operated corneas became swollen and cloudy due to destruction of the endothelium (whose function was understood later). The greatest pioneer of radial keratotomy (RK) was Dr. Fyordorov in the former USSR. In the early 1960's he converted the incisions to the front of the cornea, by making cuts 90 percent through the thickness of the cornea. He was able to devise a system of correction for different degrees of near-sightedness by making the cuts longer or shorter. From 1978–80, Drs. Leo Bores, et al, improved RK by devising ways to account for astigmatism. RK reached its peak in the mid-1980's to early 1990's.
In 1963, in the Barraquer ophthalmologic clinic (Bogotá, Colombia) Ignacio Barraquer developed the first proficient technique of refractive surgery, called keratomileusis (from the Greek Kerato: cornea and Mileusis: to sculpt) meaning corneal reshaping. Keratomileusis allowed the correction not only of myopia but also of hyperopia. The early surgeries were done by removing a corneal layer, freezing it so that it can be manually sculpted in the required shape and finally reimplanting the layer (keratomileusis with freezing). In 1986 Dr Swinger improved the surgery (keratomileusis without freezing) but it was still a slightly imprecise technique. In 1958 Arthur Schawlow and Townes, from Bell laboratories published their theory of stimuled emission of shorter wavelengths of light, which gave place to the development of Laser. In 1975 experiments with laser using a mix of argon and fluor ended with the invention of the Excimer. This Laser was used for industrial purposes. In 1980, R. Srinivasan, a scientist of IBM who was using the excimer to make microscopic circuits in microchips for informative equipments, discovered that the excimer could also be used to cut organic tissues with high accuracy without significant thermal damage.
In 1983 Stephen Trokel, scientist of Columbia University in collaboration with Srinivasan performed the Photorefractive Keratectomy (PRK) or keratomileusis in situ (without separation of corneal layer) which was more technically exact, but the patients reported it to be very uncomfortable. Also a delay in the healing was observed. The first phototherapeutic keratectomy (a procedure for removing superficial scars from the cornea) in a sighted eye was performed in 1985 by Dr. Theo Seiler in Germany. Dr. Margeurite McDonald accidentally perfomed the first successful photorefractive keratectomy (PRK) in June of 1987. While performing one of the initial studies on patients with blind eyes, one of the subjects miraculously recovered her vision seven weeks after surgery. The patient apparently had a sudden reversal of hysterical blindness, a condition originally described by Freud. She was 20/20 upon the return of her vision and remained so in the years to follow. Dr. McDonald also performed the first PRK on a sighted eye (within an FDA trial) in 1988. Improvements in the excimer laser over the past 15 years have been made in the area treated, the homogeneity of the laser beam itself, and the addition of infrared tracking of the pupil to follow any eye movement during the procedure.
The combination of Ignacio Barraquer work and the introduction of the excimer lasers lead to a new surgical technique. Ioannis Pallikaris, M.D. coined the term LASIK (laser-assisted in-situ keratomileusis), and was the first to create a “flap” of the tissue with the microkeratome, rather than to remove the entire top layer (Fig. 1.1). He conducted the first animal trials of what is now modern LASIK in the late 1980's in his native Greece. Today LASIK is the dominant corneal refractive technique used to correct ammetropias around the world. Improvements in the creation of corneal flap continue with the improved keratome reliability. Today's microkeratomes have the ability to create 90 µm thick flaps with a high degree of repeatability and safety. Flap creation has further improved after the introduction of femptosecond laser technology.
 
LAMELLAR TECHNIQUES
 
Keratomileusis in situ
Was the first developed in the 1940's. The procedure involved raising a corneal cap and the removal of corneal 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.5
zoom view
Fig. 1.1: LASIk. Note the flap created(Courtesy Dr Agarwal's Eye Hospital, India)
The refractive cut was attempted by removing stroma from the bed with a second pass of the knife or keratome. As a result the anterior corneal curvature was flettened, and therefore the myopic refractive error was reduced.1 Due to the many technical difficulties of this procedure, which were hard to overcome with the instrumentation available at the time, keratomileusis in situ had to be temporarily abandoned.1
 
Keratophakia
Barraquer did not abandon his efforts to perfect lamellar techniques. His ingenuity and persistence led to the development of keratophakia (KF), which was introduced in 1961.2 KF resulted to steepening of the central corneal curvature by placing a disk of tissue under the lamellar cap. The disk of tissue at that time was 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 on the attempted correction. KF attracted the attention of the ophthalmic community as a possible solution in the treatment of aphakia after cataract surgery.3 With the evolution and improvements of IOL technology, the interest in KF subsided, since IOLs demonstrated more accurate refractive results without the technical difficulties of harvesting the donor tissue and performing the lamellar cut.
 
Freeze Myopic Keratomileusis
In order 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; as a result freeze keratomileusis was introduced.2–5 This new technique could be used to correct myopic and hyperopic refractive errors. Barraquer found myopic corrections more successful and thus he focused his research on refining the freeze myopic keratomileusis (MKM) technique. He 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 the depth of the cut.1 Barraquer's effort for more predictable, reproducible and accurate cuts, led to the development of applanator lenses, suction rings of various diameters and various heights of microkeratome tracks.4 This work constituted the basis for future microkeratome evolution.
Even though the first reported results concerning freeze MKM were encouraging,1 freeze MKM had two major disadvantages. The cryolathe was too expensive to obtain and too complex to maintain and the learning curve was too steep, involving high rate if complications such as irregular astigmatism or corneal scarring.5
During the time, other techniques were introduced for the correction of refractive errors, such as epikeratophakia,3,6–11 incisional keratotomy12–14 and IOL implantation.15
 
Epikeratophakia
Also known as epikeratoplasty, this was introduced by Kaufman and Werblin in 1979.6 In an effort to avoid the use of 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 6a 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.9–11 Its major advantages were simplicity and reversibility. Unfortunately, the initial reports revealed that the technique was neither predictable nor safe.15 Several modifications were proposed in an effort to improve epikeratophakia.16,17 Burrato and Ferrari used the BKS system and Altmann used the excimer laser to shape epilenticles without freezing.18 However, as the difficulties could not be solved, epikeratoplasty was withdrawn from the market and research turned once again towards keratomileusis techniques.
 
Barraquer Krumeich Swinger (BKS) Technique
Due to complications that were demonstrated when using the epikeratoplasty and freeze MKM, investigations in the direction of developing nonfreezing techniques led to development of the Barraquer Krumeich Swinger (BKS) technique in 1985.19 BKS included an improved microkeratome, a set of dyes and a suction stand. The microkeratome was used to perform a total lamellar cut. The cap was then placed epithelial side down, on one of the suction dyes for the microkeratome to perform the second 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 of their technical difficulty, nonfreezing techniques proved to have a major advantage; rapid and comfortable recovery of the patients. This was attributed to the preservation of fibroblasts and corneal epithelium. However, significant amount of irregular astigmatism could not be avoided.20
In 1987, Leo Bores performed the first keratomileusis in situ in the US.21 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.22 Research began in the direction of developing new improved microkeratomes in an effort to improve the reproductibility and accuracy of the in situ technique.23
 
Automated Lamellar Keratoplasty (ALK)
The development of the automated geared microkeratome by Ruiz in 1980's 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 cut was adjusted by altering the hight of the suction ring.
ALK was a breakthrough for lamellar surgery. Initially, the corneal cap was sutured back to the stromal bed, but very soon suturing was abandoned as it was proved unnecessary. The total operative time was reduced significantly and the procedure could be safely performed under topical anesthesia. Recovery time also improved. ALK was adopted by many surgeons since it overcame the use of manual microkeratomes.
The first clinical trials on ALK revealed its advantages: (1) Easy to use, (2) Rapid recovery and stability of refraction, and (3) Efficacy in the correction of high myopia. Major disadvantages, however, were the relative high rate of irregular astigmatism (2%) and the poor predictability of the procedure (within 2 diopters).24 The later was attributed to the imprecision of the depth obtained with the second disk. Research was then focused on improving the accuracy of the second disk resection. It was at that time when thoughts of combining the precision of photorefractive keratectomy (PRK) with ALK came in the forefront.
Trokel et al suggested PRK in 1983.25 As the use of the 193 nm excimer laser in refractive surgery generated, it was revealed that for myopias greater than 6 diopters, PRK resulted in significant central corneal haze, regression of refractive effect and poor predictability.267
 
Laser in Situ Keratomileusis (LASIK)
LASIK was introduced, designed and developed at the Institute of Vision and Optics (University of Crete, Department of Medicine) in 1988.27 The term LASIK was used 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 1966.28 He attempted to do the cut manually and cut 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, with submicron accuracy of stromal tissue removal. The initial hypothesis was that a flap would assure better fitting of tissue after removing the intrastromal tissue with laser and would not affect the anatomic relations of corneal layers; since the Bowmans layer and also the subepithelial nerve plexus were preserved.
The first animal studies to determine wound healing reactions after LASIK, began in 1987, using a Lamda Physic excimer laser and a specially designed microkeratome which was able to produce a 150 microns thick 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.29
The first papers concerning LASIK were presented in Zurich in August 1989 and published in 1990.29 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
In 1992, Lucio Burrato reported the excimer laser intrastomal 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.30
Stephen Slade and Brint were the first to perform LASIK in the US in 1992. During the 1993 AAO meeting, George O Waring gave LASIK the temporary name ‘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: (1) Minimal postoperative discomfort, (2) Early recovery of visual function, (3) Lack of adverse healing phenomena such as haze formation, (4) Increased range of efficacy over PRK in myopia, hyperopia and astigmatism.
LASIK is the most recent step in the evolution of lamellar corneal techniques, initiated by Barraquer 50 years ago. Reports of 10 postoperative LASIK were encouraging, demonstrating good predictability and stability of refractive outcomes.31,32
 
SURFACE TECHNIQUES
 
Photorefractive Keratectomy (PRK)
After Trokel and Srinivasan demonstrated a new form of laser–tissue interaction, photoablation, in 198325 doctor McDonald and co-workers treated the first sighted human eye in 1988. PRK is the sculpting of the de-epithelialized corneal surface to alter refractive power. Due to the wound healing response of the cornea which leads to refractive regression and haze formation especially in high attempted corrections the popularity of PRK faded when LASIK began to be performed in the late 1990s.
 
PRK Mitomycin C and Epi-LASIK
In last few years the refractive surgery community has a shift to surface treatments in order to avoid complication of LASIK.33 Furthermore, in order to avoid PRK complications such as corneal haze, new surgical techniques and pharmaceutical aids have been introduced. These advanced surface ablation techniques include Epi-LASIK and PRK with the intraoperative use of MMC.
Nine years after experimental studies on rabbit corneas,34 the first clinical study of PRK with adjuvant MMC in 2001 demonstrated satisfactory refractive outcomes by modulating corneal healing and controlling haze formation.358
zoom view
Fig. 1.2: Epilasik separator
Today the use of MMC during PRK has become common practice, despite the inhibition of haze formation by MMC's cytostatic action, concerns regarding its adverse effects on different ocular tissues and its long term safety have been raised.36 For instance, the effect of MMC on the endothelial cell density has been controversial. Even though most reports do not demonstrate a significant change in endothelial cell density after PRK with MMC,37 there has been one report suggesting a significant decrease.38
Epipolis laser in situ keratomileusis (Epilasik) refers to an alternative surgical approach for epithelial separation by mechanical means. With this technique, the epithelial separation is performed using an instrument (Fig. 1.2) that was initially designed at the University of Crete and operates in a manner similar to that of a microkeratome.39 (The epithelial flap after stromal ablation is placed on the corneal surface reducing patient discomfort postoperatively and modulating the wound healing response of the cornea).40
 
SUMMARY
Reviewing the history of refractive surgery is essential for better understanding and future refining of the currently used techniques. Continuing evolution in all fields of refractive surgery is an obligation of all ophthalmologists, since it's the only way to approach the ultimate goal, to offer our patients a better vision both qualitatively and quantitatively.
REFERENCES
  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. Littman H. Optic of Barraquer's keratomileusis. Arch Oftal Optom 1966;6:1.
  1. Werblin TP, Klyce SD. Epikeratophakia, the correction of aphakia: 1, lathing corneal tissue. Curr Eye Res 1981;1:591–7.
  1. Barraquer JI. Modification of refraction by means of intra-corneal 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;93:342–7.
  1. Werblin TP, Blaydes JE, Kaufmann HE. Epikeratophakia, the correction of astigmatism: preliminary experimental results. CLAOJ 1983;9:61–3.
  1. Bores LD, Myers W, Cowden J. Radial keratotomy, an analysis of the American experience. Am Ophthalmol 1981;13:941–8.
  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. Mc Donald MB, Kaufamann HE, Aquavella JV, et al. The nationwide study of epikeratophakia for myopia in adults. Am J Ophthalmol 1987;103:350–65.
  1. Slade SG, Strauss GH. Use of tissue adhesive in epikeratophakia. Invest Ophthalmol Vis Sci 1990;31:30.
  1. Goosey JD, Prager TC, Marvelli TL, et al. Epikeratophakia without annular keratectomy. Am Ophthalmol 1987;19: 388–91.
  1. Altamann 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. 9 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, keratosmileusis and minus power anterior chamber lenses. Refract Corneal Surg 1990;6:245–51.
  1. Bores L. Lamellar refractive surgery. In Bores L (Ed): Refract Eye Surgery. Blackwell Publications:  Boston  1993;324–92.
  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):1092–3.
  1. Trokel S, Shrinisavan R, Braven B. Excimer laser surgery of the cornea. Am J Ophthalmol 1983;94:125.
  1. Seiler T, McDonnell PJ. Excimer laser photorefractive keratectomy. Surv Ophthalmol 1995;94:125.
  1. Pallikaris I, Papatzanaki M, Stathi EZ, et al. Laser in situ keratomileusis. Laser Surg Med 1990;10:463–8.
  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 M, 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;113:291–5.
  1. Kymionis GD, Tsiklis NS, Astyrakakis NI, et al. Elevenyear follow-up of laser in situ keratomileusis. J Cataract Refract Surg 2007;33:191–6.
  1. Alio JL, Muftuoglu O, Ortiz D, et al. Ten-year follow-up of laser in situ keratomileusis for myopia of up to −10 diopters. Am J Ophthalmol 2008;145(1):46–54.
  1. Melki SA, Azar DT. LASIK complications: etiology, management, and prevention. Survey of Ophthalmol 2001;46:95–116.
  1. Talamo JH, Gollamudi S, Green WR, et al. Modulation of corneal wound healing after excimer laser keratomileusis using topical mitomycin-C and steroids. Arch Ophthalmol 1991;109:1141–6.
  1. Majmudar PA, Forstot SL, Nirankari VS, et al. Topical mitomcyin-C for subepithelial fibrosis after corneal surgery. Ophthalmology 2000;107:89–94.
  1. Rubinfeld RS, Pfister RR, Stein RM, Foster CS, Martin NF, Stoleru S, et al. Serious complications of topical mitomycin-C after pterigium surgery. Ophthalmology 1992;99:1647–54.
  1. Diakonis VF, Pallikaris AI, Kymionis GD, et al. Alterations in endothelial cell density after photorefractive keratectomy with adjuvant mitomycin. Am J Ophthalmol 2007;144(1):99–103.
  1. Morales AJ, Zadok D, Mora-Retana R, et al. Intraoperative mitomycin and corneal endothelium after photorefractive keratectomy. Am J Ophthalmol 2006;142(3): 400–4.
  1. Pallikaris IG, Katsanevaki VJ, Kalyvianaki MI, et al. Advances in subepithelial excimer refractive surgery techniques: epi-LASIK. Curr Opin Ophthalmol 2003;14: 207–12.
  1. Katsanevaki VJ, Kalyvianaki MI, Kavroulaki DS, et al. One year clinical results after Epi LASIK for myopia. Ophthalmology 2007;114(6):1111–7.