LASIK Problems Reduced With New Laser
Larger Treatment Zone Lowers Risk of Problems in Patients With Large Pupils
July 24, 2003 -- Patients who had faced the highest risk of LASIK-caused complications -- or were turned down altogether for the popular vision-correction procedure because of their pupil size -- can now have it done safely, thanks to a new type of laser.
A new study, published in the July issue of Ophthalmology, shows that the new LADARVision 4000 excimer laser can be used safely and effectively on people whose pupil size is larger than 6 millimeters, as measured in darkness with special ophthalmic instruments. In the past, these patients were either discouraged from having LASIK, or if they had it, faced a much higher rate of postoperative problems, such as glare, halos, and poor night vision.
In LASIK, or laser-assisted in situ keratomileusis, the cornea, or clear outer covering the eye, is permanently reshaped to clear blurred vision and eliminate the need for glasses or contact lenses in those who are nearsighted, farsighted, or have astigmatism. The 15-minute procedure is done in two steps: A knife called a microkeratome is first used to cut a thin, circular flap in the cornea, which is then folded back to give the surgeon access to the cornea. Then, an excimer laser removes tiny bits of the cornea to reshape it to allow for crisp vision, and the flap is then laid back into place.
Overall, about 5% of all patients who undergo LASIK have postsurgery problems, and it's often those whose pupil diameter is large. Pupils are the seemingly black part of the eye located behind the cornea that expand in dim settings to allow more light to enter.
Other excimer lasers can be used only when the pupil size is no more than 6 millimeters, says study researcher Brian S. Boxer Wachler, MD, of the Jules Stein Eye Institute at UCLA. But the LADARVision laser allows people with larger pupils to get LASIK and still avoid the night vision problems.
"About half the population has a pupil size larger than 6 millimeters, and many of these people were turned down or considered bad candidates for LASIK," he tells WebMD. "But not everybody who should have been turned away was turned away. And they are the ones who usually wind up getting halos."
But in his study of 186 patients, many with larger-sized pupils fared better than those with the standard 6-millimeter surgical area. Overall, about 56% of patients with nearsightedness achieved vision of 20/20 or better, as did 62% of patients with nearsightedness and astigmatism. In the U.S., about 80% of patients achieve vision of at least 20/40 with LASIK.
"The take-home message is that if you've been turned down as a LASIK candidate because of pupil size, you can have the procedure with a larger treatment zone. Or if you have haloes or glare as a result of having the procedure, they can be fixed," says Boxer Wachler. "Unfortunately, LADARVision is the only laser right now that can be used to do it, and since it's so advanced and very expensive, not many surgeons currently have it."