|MEDICAL HISTORY PAGE
|Year : 2017 | Volume
| Issue : 2 | Page : 100-103
Evolution of refractive surgeries
Madhurima K Nayak
Ophthalmologist, Mangalore, Karnataka, India
|Date of Web Publication||7-Aug-2017|
Madhurima K Nayak
B-9, KMC Staff Quarters, Light House Hill Road, Mangalore, Karnataka
Source of Support: None, Conflict of Interest: None
The use of surgical procedures to correct refractive errors of the eye has come a long way. The two main types are corneal procedures and intraocular procedures. Corneal procedures have evolved from thermokeratoplasty, keratotomies, epikeratoplasty, laser ablation, conductive keratoplasty, and collagen cross-linking. Intraocular procedures involve phakic intraocular lens (IOL), toric IOL, refractive lens exchange, and accommodating IOLs. Various physicists and ophthalmologists have played a role in this saga. From the idea of using thermal energy to shrink corneal tissue to using femtosecond laser, this article highlights the important landmarks in the history of evolution of refractive surgeries. Refractive surgeries form an ever-growing specialty of ophthalmology with addition of novel techniques with every quantum of time.
Keywords: Femtosecond laser, laser-assisted in situ keratomileusis, phakic intraocular lens, photoablation, wavefront
|How to cite this article:|
Nayak MK. Evolution of refractive surgeries. Muller J Med Sci Res 2017;8:100-3
| Introduction|| |
Refractive surgeries involve procedures in various tissues of the eye to correct ametropia. These include corneal procedures and intraocular procedures. [Table 1] shows various refractive procedures available at the surgeon's disposal. Their evolution has come a long way with respect to imaging, instrumentation, and therapeutics. This article highlights the magical journey of the evolution of various refractive procedures seen in the last century. Major landmarks in the evolution of refractive surgeries are shown in [Graph 1].
It all began with a Dutch medical student, Lans, who proposed to alter the shape of the cornea using heat in 1898. Sooner, in the year 1900, he was followed by Terrien, who reported the use of cautery to correct severe astigmatism in Terrien's marginal degeneration. A paper published by Knapp in the year 1900 reported the use of galvanic current for the treatment of keratoconus and its success in improving visual acuity in 1892. In 1975, a novel method thermokeratoplasty was introduced by Shaw and Gasset with the use of a handheld probe and the temperature at which corneal tissue shrinks without undergoing denaturation (65°C) was determined.
While developments were happening in the field of using thermal energy to treat refractive errors, corneal incisional methods also saw a rise in the form of radial keratotomy. In 1936, a Japanese scientist Tsutomu Sato used corneal incisions to treat keratoconus. A Russian ophthalmologist, Fyodrov, used radial incisions extending from the pupillary area to the periphery of the cornea of varying depths to treat myopia, which was a great success. In the Prospective Evaluation of Radial Keratotomy (PERK) study, 693 eyes of 374 patients who underwent radial keratotomy in the years 1982–1983 were followed up for 10 years reporting an elimination of distance optical correction in 70% of the patients, while hyperopic shift was a major concern.
Epikeratoplasty was another novel concept of using a preserved corneal lenticule to mainly treat aphakia developed by Kaufman and Werblin et al. in the early 1980s. Later, this procedure was used to treat hyperopia, myopia, and keratoconus. However, the outcomes varied depending on the surgeon's skills, and this procedure was replaced by other more reliable procedures and now, epikeratoplasty remains of historic interest. The idea of intrastromal corneal ring segments (ICRS) was conceived in 1978 by AE Reynolds. In the early 1990s, ICRS received the Food and Drug Administration (FDA) approval for myopia. They mainly act by flattening the cornea and decreasing curvatural myopia. Today, ICRS finds its main indication in the treatment of keratoconus.
The invention of excimer laser (“Excited Dimer”) opened a new chapter in the history of refractive surgeries. It was formed by argon, krypton, or xenon in combination with a fluoride or chloride. An Indian engineer, R Srinivasan has to be credited for understanding the properties of Ecimer Laser. The 193 nm argon-fluoride is used for photoablation to create a new radius of curvature in the corneal stroma. In 1983, Stephen Trokel, a scientist at Columbia University, in collaboration with Srinivasan, performed the first photorefractive keratectomy (PRK) in Germany. PRK is surface ablation whereas, laser-assisted in situ keratomileusis (LASIK) involves creating a flap (using a microkeratome or femtosecond laser) in the superficial part of cornea and retracting it to expose the stromal bed, and then using an excimer laser to ablate the exposed surface to the desired shape, and then replacing the flap. This was first done by Ioannis Pillakaris and Lucio Burrato and loosely called it “Flap and zap.” The 193 nm photon has the ability to break carbon-carbon and carbon-nitrogen bonds that form the backbone of collagen in the cornea. In the late 1990s, LASIK gained popularity over PRK due to less postoperative discomfort and faster visual recovery. In 1995, excimer laser gained approval in the United States.
| Wavefront-guided Laser-assisted In situ Keratomileusis|| |
Wavefront technology was developed in 1999. Wavefront is the plane containing rays reflected from a point source in the retina and is recorded using an aberrometer. In a perfect optical system, it is flat. The aberrations generated are of lower order (myopia, astigmatism, and hyperopia) and higher order (coma, trefoil, quadrofoil, and spherical aberration). The higher-order aberrations increase with pupillary dilatation, miosis or following a conventional PRK/LASIK. The result of these is a degraded image quality. Wavefront-guided and wavefront-optimized LASIK are gaining popularity as these aberrations are recognized using an aberrometer and LASIK is then performed accordingly. A better image is produced postoperatively. It gained FDA approval in 2002. Another development in LASIK is postoperative use of topical Mitomycin C. It was suggested by Talamo et al. due to its effects seen in rabbit corneas after surface ablation. It is found to reduce haze when applied at a dose of 0.02%. In addition, it controls over correction of refractive error.
Epipolis LASIK (Epilasik) and laser epithelial keratomileusis (LASEK) are epithelium preserving methods. In the former, an epithelial flap is raised (without involving the stroma), and it successfully adheres postoperatively. In the latter, an alcohol-tipped applicator is used to loosen the epithelium and ablation is carried out.
The principle of collagen shrinkage using heat was mainly used for laser thermokeratoplasty, in which Holmium:Yttrium-Aluminium-Garnet laser was approved for hyperopic correction in 2000. However, its use is on the decline due to significant regression of refractive error. Another application is conductive keratoplasty, in which radiofrequency energy is used for treating small degrees of hyperopia and presbyopia. It found FDA approval for use in hyperopia in 2002. Corneal collagen cross-linking was first described in 1997 and it involves application of riboflavin to the corneal stroma and exposing it to ultraviolet-A radiation. However, its use is reserved for treating ectatic conditions of cornea.
| Intraocular Surgery|| |
Although the concept of use of angle-supported phakic intraocular lens (IOLs) for myopia was started by Strampelli and Barraquer in the late 1950s, it saw a new phase during the 1980s. They received FDA approval in 2004. Fechner and Worst introduced a phakic myopia lens of iris-claw design in 1986. In addition, posterior chamber phakic IOLs were developed in 1986 which were made from Collamer (copolymer of porcine collagen and hydroxyethyl methacrylate). Phakic IOLs have their role in correcting higher degrees of refractive error. The concept of “Bioptics” was introduced by Zaldivar et al. at the turn of the millennium in which high degrees of myopia are first corrected using posterior chamber phakic IOL followed by LASIK correction of residual myopia/astigmatism. Around the same time, Güell came up with adjustable refractive surgery, the idea of creating a corneal flap just prior to the intraocular procedure of inserting the phakic IOL and then planning the necessary ablation required depending on the residual refractive error at a later point in time. Refractive lens exchange is indicated only if other modalities are not feasible. Use of toric IOLs, multifocals, and accommodative IOLs are recent advances in this field.
| The “Femtosecond” Era|| |
Femtosecond laser technology uses near infrared radiation (1053 nm) from neodymium: Glass to cause photodisruption. When it interacts with tissue, it causes plasma formation. This plasma of free electrons and ionized molecules expands rapidly to cause cavitation bubbles and separate tissue. It gets its name from the speed at which light is delivered (10−15 s). As a result, collateral damage of surrounding tissues and heat generation is almost nil. Femtosecond laser finds its use in creation of flaps for LASIK and tunnels for ICRS insertion. Microkeratome-related problems are avoided and precision is maintained. Its use is extended for small incision lenticule extraction (SMILE) as well.
| Small Incision Lenticule Extraction|| |
SMILE is acronym for small incision lenticule extraction and was introduced in 2007. In this procedure, an intrastromal lenticule is extracted through a 2–3 mm long incision created using femtosecond laser [Figure 1]. The commencement of this procedure began in September 2011 and is established in various locations such as Europe, China, and India. It is gaining importance as it is minimally invasive, flapless, promising refractive surgery.
|Figure 1: Incision geometry of the small incision lenticule extraction procedure|
Click here to view
Thus, a wide array of choices of refractive surgeries is available, mostly dominated by LASIK, even today. This is one of the fields in which revolutionary techniques have brought about highly satisfying results.
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Conflicts of interest
There are no conflicts of interest.
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