Glaucoma damage is common in whites, studies show

Whites may be at higher risk of blindness from open-angle glaucoma than previously thought.

ROCHESTER, U.S.A. — A study by Mayo Clinic researchers, published in the November 1998 issue of Ophthalmology, concludes that the risk of blindness from open-angle glaucoma among whites, despite treatment, may be significantly higher than previously thought.

Matthew G. Hattenhauer, MD, and colleagues at the Mayo Clinic conducted a retrospective, community-based descriptive study of 259 patients treated for open-angle glaucoma between 1965 and 1980.

The study was done through the Rochester Epidemiology Project, which was conducted by two medical facilities in Olmsted County here in Minnesota. The study defined legal blindness as less than 20/200 visual acuity and/or a visual field less than 20°.

The study showed that the risk of developing blindness from open-angle glaucoma, despite treatment, may be considerable in a non-referred, community-based white population.

The probability of blindness in at least one eye of patients newly diagnosed and treated with medical or surgical therapy was 27%, according to the study. The probability of blindness in both eyes was 9% at 20 years.

Patients with open-angle glaucoma at the time of diagnosis (evidence of optic disc and/or visual field loss consistent with glaucoma) had a 22% probability of blindness in both eyes and a 54% probability of blindness in at least one eye at 20 years.

However, those treated for ocular hypertension at the time of diagnosis without evidence of glaucomatous optic disc and/or visual field loss had an estimated probability of blindness in both eyes of 4%, and in at least one eye of 14%.

"People can and do go blind from glaucoma even while receiving treatment," Dr. Hattenhauer said. "Those who are diagnosed after damage has occurred are at greater risk. This study may affect physicians’ decisions regarding therapeutic options."

Treatment justified

The normal tension study concluded that intraocular pressure (IOP) causes damage to the visual field in normal tension glaucoma.

The authors studied 140 eyes in 140 patients, using 61 as study and 79 as untreated controls. In the follow-up, 28 control eyes (35%) and 7 treated eyes (12%) reached the defined level of optic disc progression or loss of visual field.

According to Alan S. Crandall, MD, a glaucoma specialist in Salt Lake City, U.S.A., the two studies show that patients need aggressive treatment of glaucoma to preserve vision.

"There have been a number of publications this year that are of major importance in the question of IOP management," Dr. Crandall said. "Everything that we’ve done in the past is based on the assumption that treatment helps. There’s never been proof of that, and now there is."

Because some patients did go blind, all patients were overtreated, with no evidence that lowering pressure had any effect. The two studies prove that hypothesis wrong, he added.

"In this day and age, where people are living longer, if you’ve got an unhealthy optic nerve in a relatively young person, you’ve got to shoot for low pressure quicker and maintain those pressures over a long period of time," he said.

For Your Information:

Matthew G. Hattenhauer, MD, is an assistant professor of ophthalmology at the Mayo Clinic, Department of Ophthalmology, 2001 First St. SW, Rochester, MN 55905 U.S.A.; +(001) 507-284-4567; fax: +(001) 507-284-4612.

Alan S. Crandall, MD, practices at the John Moran Eye Center, 50 N. Medical Drive, Salt Lake City, UT 84132 U.S.A.; +(001) 801-581-2769; fax: +(001) 801-581-3357; e-mail: alan.crandall@hsc.utah.edu. Neither doctor has a direct financial interest in the products mentioned in this article, nor is either a paid consultant for any companies mentioned.