Some of the 10 million Americans with substantial nearsightedness or astigmatism may soon have another alternative to eye glasses and contact lenses.

Until now, laser vision correction, also known as photorefractive keratectomy (PRK), has only been approved for treating low to moderate nearsightedness and astigmatism. But recent developments suggest that laser treatment for people with severe cases of these eye disorders may soon be available.

Of the 50 million Americans with nearsightedness--also known as myopia--approximately one in five falls into the range classified as severe. People with nearsightedness have blurred or distorted distant vision. Pronounced astigmatism, in which near and far vision is distorted or blurred, occurs in two-thirds of people with nearsightedness.

Preliminary results of a study evaluating a new excimer laser that may allow treatment for more significant degrees of nearsightedness and astigmatism are promising, according to David Hwang, MD, UCSF associate professor of ophthalmology.

Hwang, principal investigator of an FDA phase III clinical trial of the Nidek excimer laser, reported the interim results at a media briefing held yesterday in conjunction with the American Academy of Ophthalmology annual meeting in San Francisco.

In the national multicenter study, Hwang reported, 91 percent of 148 patients with nearsightedness ranging from mild to severe achieved vision of 20/40 or better after being treated with the Nidek laser--good enough to pass a driver's test without corrective lenses. Glasses or contacts were still required in the remaining 9 percent of patients, but the amount of lens correction was substantially reduced as a result of the laser treatment.

"This finding suggests that the door may soon open for many people who couldn't previously be treated with laser therapy," says Hwang, co-director of the UCSF Vision Correction Center.

The Nidek laser, still being evaluated, differs from existing, FDA-approved excimer lasers such as the VISX laser, which currently is the only laser approved for treating low to moderate nearsightedness and astigmatism. Whereas the VISX laser utilizes a beam of fixed diameter and position, the Nidek laser scans across a wider surface of the cornea, producing a smoother sculpting of the cornea. This procedure can translate into improved accuracy, particularly in severely nearsighted cases.

The results of the VISX laser at UCSF for treating low to moderate nearsightedness and astigmatism have been excellent," says Hwang, "and the Nidek excimer laser promises an even greater level of accuracy in severe cases."

UCSF is the only center in California that has both the Nidek excimer laser and the VISX laser. Enrollment in the Nidek laser study is still ongoing.

FDA approval of the Nidek laser is at least 18 to 24 months away, Hwang estimates. Meanwhile, VISX, Inc., of Santa Clara, CA, earlier this month filed an application with the FDA seeking extension of the approved use of its laser to include more severe degrees of nearsightedness.

Photorefractive keratectomy involves reshaping the curvature of the cornea, the transparent window of the eye that covers the iris and the pupil and admits light into the eye's interior. A normal cornea is round, like a basketball, and focuses light rays directly onto the retina.

In people with astigmatism, the cornea is warped, curving more in one direction than the other, like a football. This defect blurs or distorts both near and distant vision, and can make objects appear too tall, too wide or too thin. Nearsighted vision is caused by a steeper curvature in the cornea, which forces light rays to focus in front of the retina, resulting in blurred or distorted distant vision.

The excimer laser is used to remove microscopic amounts of tissue from the surface of the cornea, making the central zone flatter. The flattened cornea is thus able to focus light more directly on the retina, reducing astigmatism and nearsightedness. The laser system's computer-controlled technology calculates the exact amount of corneal tissue to be removed, which typically is less than a strand of human hair.

Because of the precision of the computer system, the excimer laser does not penetrate the eye and leaves other areas of the eye undisturbed. The entire treatment takes less than 15 minutes; the excimer laser itself is used for less than 60 seconds.

Astigmatic and nearsighted patients may qualify for the UCSF Nidek laser study if they are over the age of 21, have two healthy eyes and a best corrected vision of 20/40 or better in both eyes. Patients must have a vision problem of between 1 and 4 diopters of astigmatism and have no more than 15 diopters of nearsightedness. They must be available for two years of follow-up study. There is a cost to the patient to enroll in the study.

For more information or to attend a free information seminar, people should call (415) 476-5021. Information is also available at the Vision Correction Center website .

By Jennifer O’Brien

1st appeared 10/29/97

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