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U.S. Food and Drug Administration |
This article originally appeared in the July-August 1995 FDA Consumer and contains revisions made in November 1995 and December 1996. The article is no longer being updated. For additional information, see LASIK Eye Surgery on this Website. |
"Men seldom make passes at girls who wear glasses," Dorothy Parker observed in 1926. True or not, when the writer penned her now famous line, the only alternative to glasses was poor sight. Things are rosier--but not perfect--at the close of the century.
Today, growing numbers of women and men alike are opting for refractive eye surgery to correct their myopia (nearsightedness) in hopes of abandoning their glasses or contact lenses. The most common procedure is called radial keratotomy, or RK, and the National Eye Institute says about 250,000 are done each year in the United States, up from 30,000 in 1990.
Another surgery, newly available in the United States, is photorefractive keratectomy, or PRK. In October 1995, the Food and Drug Administration approved the Summit Apex excimer laser system for use in this procedure. A report by the American Academy of Ophthalmology published in the July 7, 1993, issue of Ophthalmology indicates that cosmetic reasons are not at the top of the list of reasons why people choose to have refractive surgery. The report states: "In two studies, approximately 75 percent of the patients who were interviewed about their reasons for seeking radial keratotomy stated that they wished to see well without physical dependence on ... spectacles or contact lenses. Patients also sought radial keratotomy to improve their performance in profession or sport, to improve cosmetic appearance, for simple convenience, or at times to meet the visual requirements for occupations such as law enforcement and firefighting."
David Euley, a 52-year-old Darnestown, Md., kitchen designer and home remodeler, began to consider RK when he found himself becoming increasingly frustrated with his glasses, particularly at work. "It was difficult to go back and forth from blueprints to taking measurements to working on a computer," he says, adding that he needed a separate prescription for computer work.
Euley talked with several ophthalmologists before deciding to have the surgery last December. Interviewed four months later, he was delighted with the results: "This is the first time in 25 years I've been able to see the titles on television without glasses. I can read license plates. I can see the deer in my backyard. And my glasses are sitting on a shelf somewhere."
Six incisions in each cornea (the clear part of the front of the eye) left Euley with uncorrected vision improved from 20/800 in both eyes to 20/20 in the right and 20/25 in the left. (A person with 20/40 vision, for example, would see an object from 20 feet that another with perfect vision--20/20--could see at 40 feet. Some people see even better than 20/20.)
RK is often done in the doctor's office. As in Euley's case, surgeries on each eye are usually scheduled a few weeks apart, as a precaution in case there are complications. The patient is given anesthetic eye drops to numb the eye. Using a high-precision diamond blade knife, the surgeon makes from four to eight spoke-like incisions in the cornea, while the patient focuses on the light of the operating microscope. The surgery takes about 10 to 15 minutes.
I Can See Clearly Now
Euley can read those license plates without glasses now because the incisions changed the shape of his corneas. Normally, the cornea and lens bend light rays to focus directly on the retina--the tissue at the back of the eye that receives the image. If the cornea or lens is too rounded, or the eyeball is elongated, the light focuses in front of the retina, blurring distant objects. RK reduces or eliminates the myopia by flattening the cornea and redirecting the light to focus on the retina.
The patient may have some pain or discomfort for 24 to 48 hours after surgery, possibly requiring medication. Glare, starbursting, or a halo effect, especially at night, is common for a few months and occasionally persists a year or more. Vision also commonly fluctuates during the day, with acuity best in the morning and diminishing somewhat at night. This decreases in severity during the first year, but may last for many years.
Notwithstanding some claims to the contrary, RK is not a cure-all. (The Federal Trade Commission is investigating the problem of misleading claims in advertisements.) Reputable ophthalmologists will tell prospective patients the procedure is not completely risk-free, and perfect vision cannot be guaranteed.
Is RK Safe and Effective?
"FDA does not regulate radial keratotomy because it is a medical procedure, not a medical device," says Emma Knight, an ophthalmologist and medical reviewer with FDA's Center for Devices and Radiological Health. "The knife used in RK had been cleared by the agency for general corneal surgery."
The National Eye Institute (NEI), however, concluded from a 10-year study called "Prospective Evaluation of Radial Keratotomy (PERK)" that RK is "reasonably safe and effective … with serious complications being rare."
All patients in the study had -2 to -8 diopters and could be corrected to 20/20 vision or better with glasses or contact lenses. (A diopter is the unit of measurement of spectacle or contact lens power. A minus value indicates nearsightedness; plus indicates farsightedness, or hyperopia. Euley's correction was -3.25 diopters.)
Results of the NEI-sponsored multicenter trial were reported by study investigator George Waring III, M.D., and colleagues in the October 1994 Archives of Ophthalmology. Among 374 patients (with 693 operated eyes) who returned for the 10-year follow-up:
The cornea is weakened by radial keratotomy, increasing the risk of eye rupture from physical trauma. According to the article by the American Academy of Ophthalmology, however, there have been reports of severe eye trauma without damage to the incision wounds. The report also says that potentially blinding complications, such as corneal infection or perforation are rare.
More recent studies using newer RK techniques have achieved better optical results, says Peter Hersh, M.D., director of keratorefractive surgery at Montefiore Hospital, Bronx, N.Y.
Surgeons have designed improved methods for calculating the number and length of incisions and the diameter of the optical zone (the central clear zone that has no cuts) that will produce the best results in a given patient, he says.
"We've had numbers reported as high as 95 percent or so for 20/40 as the procedure has evolved," Hersh says. "The most important variable is patient age. Younger patients tend to heal their incisions better and more quickly, and therefore get less of an effect. Also, patients with lower degrees of myopia do better than high myopes," he says. Some other factors that may be considered when determining surgical procedure include corneal curvature, topography and thickness, and ocular pressure.
The Laser Method
An alternative to radial keratotomy is photorefractive keratectomy, or PRK. "In countries where PRK has been available for some time, the procedure has largely replaced RK as the procedure of choice," says FDA's Knight, adding that "with FDA approval of the excimer laser, this trend is expected to follow in the United States."
In this procedure, the surgeon operates an excimer laser programmed to deliver bursts of ultraviolet light that vaporize precisely targeted corneal tissue. The effect, as in RK, is to flatten the cornea. Also like RK, PRK takes about 15 minutes and is done under topical anesthesia.
In October 1994, FDA's ophthalmic devices advisory panel recommended conditional approval of one manufacturer's excimer laser for refractive surgery, pending reformatting and reanalysis of some of the data.
"This was the first time the agency critically assessed safety and effectiveness data of any device for refractive surgery," says Knight, "and the meeting was long and full of debate."
Approval in October 1995 was based on PRK results in about 1,600 healthy myopic eyes. In most eyes, the corneal surface healed in three days, and vision took at least three months to stabilize. Most patients studied were corrected to 20/20 vision or better with glasses or contact lenses before surgery. Best corrected vision was worse in 6 percent of patients after surgery but, of those, only 1 percent had less than 20/25 acuity and fewer than 0.2 percent were worse than 20/40.
In 95 percent of eyes, vision without glasses was corrected to 20/40 or better; 65 percent achieved 20/20 or better. About 5 percent of patients continued to need glasses all the time for distance, and up to 15 percent needed glasses occasionally, such as for driving. Results were best in younger patients with lower degrees of myopia.
Some 63 percent of patients had mild corneal haze after surgery, and 10 percent experienced mild glare and halos around lights. These conditions diminished or disappeared in most patients in six months.
According to the American Academy of Ophthalmology, RK results are best in patients with low to moderate nearsightedness and generally is not recommended for people with a correction higher than -5 diopters. PRK is effective for patients with higher myopia as well, and is approved for treatment of up to -7 diopters.
With approval of the laser, FDA also reviewed and approved a physician training program and a patient information booklet. The training program for surgeons covers operation and calibration of the laser, plus extensive clinical, didactic and practical sessions. The patient booklet is provided to physicians, who in turn are required to give it to patients and discuss it with them before surgery.
Mary Taylor had her first PRK in November 1993. The highly myopic 42-year-old Winchester, Va., woman had worn glasses since second grade. Her correction was -9.5 diopters in one eye and -10 in the other.
"I tried contacts a few times, but never really got comfortable with them," she says, "and, although I didn't especially mind wearing glasses, I was bothered by how helpless I felt without them. The thought of losing them if something happened while I was driving or swimming--even if I had a spare pair--was always a worry in the back of my mind."
Taylor says she received about 700 laser bursts at periodic intervals during the procedure. Then the doctor put a soft "bandage" contact lens in her eye to be worn the next few days until the surface cells healed. She was given a nonsteroidal anti-inflammatory eyedrop for pain and a prescription for additional pain medicine, if needed.
"That first day I felt a mild discomfort, like a residual scratchiness after removing a piece of sand from the eye. It was gone when I woke up the next morning," Taylor says. Although her vision improved greatly immediately, it took about a month or two, she says, before she was seeing 20/20. Six months after the first operation, she returned for surgery in the second eye.
As of October 1994, according to Taylor's doctor, her vision was 20/25 without glasses and 20/20 with glasses, and her correction was -0.75 diopter. Taylor says she still has some trouble with night glare and needs glasses to drive at night, but she's delighted with the results. "For the first time in my life that I could remember, I could see my feet in the shower," she says.
RK vs. PRK
Jeffrey Robin, M.D., has a unique perspective on RK and PRK. Head of the department of refractive surgery at the Cleveland Clinic, Robin has done both procedures on patients in clinical trials and has, himself, undergone both procedures.
"I've worn glasses since I was eight, and started wearing contact lenses when I was 17 or 18," Robin says. "I went through many pairs of lenses--tore them, slept in them. I was not a good contact lens patient and I detested wearing my glasses, basically because I didn't perceive I was seeing well with them," he says.
About five years ago, at age 35, Robin had an 8-incisional RK in his right eye. A year later, he had PRK in the left. He felt only minor, temporary discomfort after both surgeries, but says that before anti-inflammatory drops were used with PRK, that procedure often produced intense post-surgery pain.
"With RK, vision is almost instantaneously improved--I went from about 20/800 to better than 20/20 the morning after surgery," Robin says. "After PRK, I had better than 20/20 after about 10 days to two weeks. The big difference with the laser is that the correction is solid--there's no visual fluctuations and really no starbursting like you get with RK. Except for the couple of weeks after my RK when I used night driving glasses, I haven't worn glasses since. I've almost forgotten I ever wore them."
Four years of follow-up with PRK has shown fewer complications, such as infection or cataract, than are seen with RK. Also, hyperopic shift has not been seen with PRK, nor is the cornea weakened as it is in RK. On the other hand, Robin says, "we have 15 or 16 years of experience with RK as opposed to about four years with PRK. Between 1 million and 2 million Americans have had RK and probably only 4,000 to 5,000 have had PRK, so we kind of know the warts--the good and bad sides--of RK whereas we don't really know all those things with our more limited experience with PRK."
Both refractive surgeries are considered cosmetic procedures and generally are not covered by insurance. Robin says that RK generally varies from $600 to $1,500 per eye and laser surgery costs around $2,000 per eye.
Prospects for 20/20 in 2020
Visions of a world entirely without glasses in the foreseeable future are probably premature; refractive surgery is not for everyone. "From a medical standpoint, we are most concerned about people who have wound healing problems," Robin says, "because in all these procedures, the results are ultimately affected by two things--what we do as surgeons, and then how the patient's body reacts to the laser or knife wounds."
The procedures should not be done on patients with connective tissue diseases such as rheumatoid arthritis or lupus erythematosus, or on people with uncontrolled diabetes, autoimmune disease, or some eye diseases such as poorly controlled glaucoma, macular disease, retinal problems, extremely dry eyes, and certain corneal problems.
Pregnant women also should not have refractive surgery, because the refraction of the eye changes during pregnancy.
Robin, Hersh and Knight all agree that people who are not comfortable with the possibility that they may still need glasses or contact lenses at least part-time after surgery are probably not good candidates. Prospective patients should carefully weigh their hoped-for benefits against the calculated risks. After all, no surgeon can guarantee 20/20 vision except for hindsightedness.
Marian Segal is a member of FDA's public affairs staff
Despite RK's long history, refractive surgery is still in its "early toddlerhood," says Jeffrey Robin, M.D. Head of the department of refractive surgery at the Cleveland Clinic, Robin foresees a broader spectrum of procedures, pending laser approval, that will include RK, PRK, and others now under study.
"There's a growing menu of approaches that can potentially help people with a variety of refractive errors--low, moderate and high nearsightedness, farsightedness, and even presbyopia [farsightedness associated with aging]," he says, noting that surgeons are also combining the knife and laser techniques to try to achieve better accuracy and effectiveness, especially for very nearsighted people.
For example, in an experimental procedure called laser in situ keratomileusis (LASIK), the surgeon uses a knife to cut a flap of corneal tissue, lases targeted cells beneath it, and then replaces the flap.
"Possible advantages of LASIK are better results with high myopia, less chance of scarring and haze, faster recovery, and less pain than simple PRK," says FDA's Emma Knight, M.D., an ophthalmologist with the agency's Center for Devices and Radiological Health. "From FDA's standpoint, we want to know not just if LASIK is a good enough procedure, but if it is as good or better than PRK. So we've asked people to do randomized studies. We must also be sure there are not any greater risks than with standard PRK."
--M.S.
Publication No. (FDA) 97-1227
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