What is Refractive Surgery?
Refractive surgery is surgery performed on the eye to create a better focus and lesser dependence on glasses and contact lenses. In recent years the field has expanded to include operations for all types of refractive errors: myopia, hyperopia, astigmatism and presbyopia. The recent increase in popularity of refractive surgery is directly related to its success in producing effective and predictable visual improvement without significant side effects.
Strictly speaking, refractive surgery might also include procedures which have a refractive impact, e.g., cataract extraction and corneal transplantation, both of which signficantly affect the refractive error of the involved eye. However, this effect is mostly secondary to the actual purpose of the surgery, which is usually to eliminate an opacification in the normally clear line of vision. Therefore, this discussion will be limited to those procedures which possess the primary intent of lessening the refractive error of the eye.
The history of refractive surgery has its early roots in claims in the mid 1800s to eliminate glasses by flattening the cornea with a spring-mounted mallet through the closed eyelid. However, it was a hundred years later before serious surgical investigation was begun.
- The basic principles of keratotomy were specified by L.J. Lans, of
The Netherlands in 1898; these concepts were extended to the clinical
arena in 1940s and 1950s by T. Sato and K. Akiyam of Japan, who placed
both transverse and radial incision in the posterior surface of the
cornea.Their surgery caused the central part of the cornea to flatten,
thereby correcting myopia. They correctly observed that the amount
of correction in vision was directly related to the number, length
and depth of the incisions.
- In the 1960s in the USSR, S. Fyodorov significantly increased
the safety of what was now called Radial Keratotomy (RK) by
placing the multiple incisions on the anterior surface of the
eye and leaving a clear central optical zone. He observed that
predictable results could be obtained by using steel surgical
blades and a standardized formula of correction. Interest in
Radial Keratotomy spread to the United States in the late 1970s
prompting the nationwide PERK study sanctioned by the National
Eye Institute. Results of this study demonstrated the effectiveness
of RK but also noted a disturbing percentage of patients with
progressive surgical effect and fluctuating daily vision.
- Improvements in RK surgical technology by the use of ultrathin diamond micrometer cutting blades, microscopic guidance systems and computer databases for results tracking and predictive nomograms helped the procedure to become increasing popular in the early 1990s after a dropoff in popularity owing to the results of the PERK study.
- During this time research into the use of the excimer laser was begun
by Charles Brau and James Ewing in 1973. The first excimer laser action
was produced by Stuart Searles in 1975; the first commercial system
was created by Tachisto in 1979. Research into ophthalmology usage
was noted by Taboada, Mikesell and Reed in 1981 who performed procedures
on the anterior corneal surface. In 1983 Stephen Trokel presented a
paper describing the potential of the excimer laser for performing
photorefractive keratectomy (PRK) on humans. The first experiments
were soon after performed by Trokel and R. Srinivasan. Shortly afterwards
in 1985 and 1986 were formed two companies, VISX and Summit Technology,
Inc., which introduced the excimer laser to the ophthalmology community
of the United States.
- In 1987 L'Esperance performed the first PRKin the United
States on a blind eye; a year later, Marguerite McDonald performed
the first PRK in the United States on a normally sighted person
with myopia. The first procedure of phototherapeutic keratectomy
(PTK) was performed by Theo Seiler of Germany in 1985.
- After a series of clinical studies, the United
States FDA finally approved the use of the
Summit laser for PRK correction of myopia in
1995; approval for the VISX laser was granted
later in 1996. A year later, the FDA approved
the use of the VISX laser for the correction
of myopic astigmatism.The Food and Drug Administration
of the United States approved the excimer laser
for Photorefractive Keratectomy (PRK) in October,
1995, for the purpose of correcting nearsightedness.
The procedure of PRK reshapes the human cornea
by application of laser energy to its front
surface, producing a flattening effect. Approval
was based on clinical trials of more than 1600
eyes followed for three years. Additional consideration
was given to studies from Canada and Europe,
where the procedure has been performed since
1987
The report responsible for FDA approval of PRK in the United States utilized a 6.0 mm central treatment zone. The multicenter studies involved 398 eyes in 300 patients. The mean attempted correction was -4.23 D with range of -1.50 D to -7.80 D. Twelve months after the procedure, 98.8% of eyes treated had 20/40 or better uncorrected visual acuity; 80.5% of eyes saw 20/20 or better. Vision was stable (as opposed to RK.) The only adverse effects were minimal symptoms of halos and glare in 2.4% of eyes and a loss of best corrected visual acuity of two lines in 1.2% of eyes. (Note: it is likely that these minimal adverse effects will disappear when the 18 month point is reached.)
The approval was recognized by the American Society of Cataract and Refractive Surgery and the International Society for Refractive Surgery which offers its members instruction and information regarding this and other evolving refractive surgical corrective techniques. TheAmerican Academy of Ophthalmology has now certified PRK as being safe and effective in correcting low and moderate levels of myopia.
- The concept of LASIK refractive surgery involves the placement of
an incision into the cornea to create a hinged flap which can then
be lifted up to expose the underlying corneal stroma which can be partially
ablated with the excimer laser. The origins of this procedure begin
with Jose Barraquer who founded the operation of Keratomileusis in
the 1970s by which a thin corneal wafer was removed, reshaped with
a cryolathe, and then reinserted into the cornea. Automated Lamellar
Keratectomy as created by Luis A. Ruiz in the 1982 took this concept
further by using an automated device called a microkeratome, or corneal
shaper, to excise an internal disc of corneal tissue allowing treatment
of myopic refractive errors up to -20 diopters.
- LASIK was originally described in 1989 by Pillikaris of Greece who used the excimer laser to treat the underlying stromal bed beneath a corneal flap which he had created with a microkeratome; a year later, Buratto of Italy used the same technique to successfully treat the undersurface of the corneal flap. The operation of LASIK became increasingly popular worldwide as its predictabiliy became enhanced and the lack of pain and rapid improvement in vision fueled consumer demand. In 1997, the FDA of the United States deemed the procedure to be 'off label' and thereby permissible to be performed by any licensed physician. After prolonged investigation into its safety and effectiveness, the FDA approved LASIK as a medical procedure in 1999. It is estimated that LASIK accounts more than 98% of all refractive surgical procedures worldwide.
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