Surgery for Nearsightedness Is Effective and Safe, Study Finds : Health: Few who underwent radial keratotomy needed distance glasses after 10 years, researchers say. But many required reading glasses sooner than expected.
Radial keratotomy, the controversial surgical technique in which slits are made in the surface of the eye to eliminate the need for glasses, is both safe and effective, according to results of a 10-year study directed by USC and sponsored by the National Eye Institute.
The study’s findings, proponents say, may put to rest concerns over the procedure. But the results also raise questions about its long-term effects.
At the end of 10 years, 70% of the 374 patients in the study still did not need glasses to correct their ability to see objects in the distance. But many did require reading glasses sooner than they would have without the surgery, according to a report to be published Friday in the Archives of Ophthalmology.
Only 3% had poorer distance vision a decade after surgery and none had catastrophic problems, the scientists reported.
Imported from the Soviet Union 16 years ago, radial keratotomy has gradually increased in popularity. It is designed to correct nearsightedness, a condition that affects about 70 million Americans.
“Based on these findings . . . some people will be pleased with their vision shortly after having RK, but their opinion may change five, 10 or 15 years down the road,” said study leader Dr. Peter J. McDonnell of USC’s Doheny Eye Institute.
“If your primary object is to get rid of your glasses, this technique will most likely be successful until you are into your 40s,” said Dr. Carl Kupfer, director of the National Eye Institute. “But as you age, you’ll be a little more likely to have to wear reading glasses. . . . This study has provided the basic information to allow a patient to make an informed decision” about whether to have the procedure.
“The big picture is that RK is a very safe way of significantly improving distance vision in a majority of people,” said Dr. Robert Maloney of UCLA’s Jules Stein Eye Institute. “The key number is that 85% of people will have vision of 20/40 or better, which is good enough to get a driver’s license” without eyeglasses.
“I think the study shows that RK is a safe and effective, although not perfect, alternative for people who don’t want to rely on glasses or contact lenses,” he said.
In nearsightedness, the cornea--the lens that focuses light on the photoreceptors of the retina--is slightly thicker in the middle than it should be. The result is that light from a distance is focused slightly in front of the retina, causing blurring.
In RK, the surgeon uses a diamond blade under a local anesthetic to make four to 16 shallow incisions in the cornea from the center to near the outer edge. These incisions cause the cornea to flatten out slightly, refocusing distant light on the retina.
The 10-minute procedure typically costs from $1,200 to $1,500 per eye in the Los Angeles area.
More than 250,000 people in the United States will have RK surgeries this year, up from 30,000 only five years ago. The highest concentration of the surgeries is in Texas, California and Florida.
The 374 subjects in the study underwent the procedure on each eye at nine centers throughout the country. Their vision was evaluated periodically--a process that is still continuing.
At the 10-year mark, 53% of the eyes had 20/20 vision and 85% had 20/40 vision or better. “People with 20/40 vision can get up in the morning and read the alarm clock without glasses, drive their car and so forth,” Maloney said. “But many of these people will still wear glasses for driving at night, for going to a movie or a play or for whenever they need to see perfectly.”
The safety demonstrated in the study is also extremely important, researchers said. When the procedure was first imported from the Soviet Union, many critics predicted occasional disastrous consequence, ranging from blindness to loss of the eye. That has not been observed in the study, and the researchers say there have been no reported instances of such complications.
Only 3% of the eyes in the study became more nearsighted after 10 years than they were before the surgery, and that decrease in vision was “very tiny,” McDonnell said. Typically, such subjects’ vision--even with glasses--would decrease by about five points, such as from 20/20 to 20/25, he said.
To the surprise of the researchers, however, 40% of the subjects became more farsighted over the course of the study, and required reading glasses three to four years earlier than they would have otherwise. But for someone who does not want to wear glasses for sports or occupational purposes, that is a fair trade-off, McDonnell said.
McDonnell added that the procedure has changed considerably since the surgeries in the study were performed. People get fewer incisions, the incisions tend to be shorter and the knives are thinner, so there is less trauma. “In some reports, 95% to 100% of the subjects have 20/40 vision or better. In the short term, that is a real improvement. The question is what will happen in another 10 years.”
Seeing Better
A 10-year study of radial keratotomy--a controversial surgical technique--has shown that the procedure is safe. More than 70% of subjects still did not need glasses for distance vision. Only 3% had poorer distance vision with glasses a decade after surgery and none had catastrophic problems.
1) Nearsightedness occurs when the cornea is too thick.
2) Surgeons make four to 16 radial incisions in the cornea that allow it to relax and become thinner, so that it focuses light correctly.
