Eye Drops Delay Onset of Glaucoma in Higher Risk Patients

Results of five-year, multi-site study prove safety and efficacy of topical medication

(Philadelphia, PA) -- Open-angle glaucoma -- the most common form of glaucoma -- is a leading cause of blindness in the United States and the number one cause of blindness in African Americans, affecting more than 2.2 million Americans age 40 and over. It occurs when the optic nerve is damaged; damage which, in most cases, is caused by elevated pressure in the eye.

However, not everyone with elevated pressure develops glaucoma and there are some who develop the disease despite having normal eye pressure.
Now, researchers at Scheie Eye Institute at the University of Pennsylvania School of Medicine, led by Jody Piltz-Seymour, MD, have determined that eye drops used to treat elevated pressure inside the eye can be effective in delaying -- and possibly preventing -- the onset of glaucoma. The results of the five-year, 22-site nationwide Ocular Hypertension Treatment Study (OHTS) appear in the June issue of the Archives of Ophthalmology.

The randomized study, which enrolled 1636 patients -- 25% of whom were African Americans -- was designed to determine the safety and effectiveness of eye drops that lower eye pressure in preventing or delaying the onset of primary open-angle glaucoma in people with elevated pressure but no evidence of glaucoma damage. The participants were divided into two groups -- one group received the eye drops, the second group received no medication but was observed throughout the duration of the study.

According to Dr. Piltz-Seymour, principal investigator of the study at the Penn site, the rate of developing glaucoma in OHTS was reduced by more than 50% in participants who were administered the eye drops.

Overall, 4.4% of the study participants who received the eye drops developed glaucoma within five years, compared to 9.5% of the study participants who did not receive the eye drops. "It is estimated that between three and six million people in the United States have elevated eye pressure, which increases their risk for developing this common form of glaucoma," explains Dr. Piltz-Seymour. "Until now, we did not know if treating elevated eye pressure -- before glaucoma developed -- could delay the onset of the disease. The results of the OHTS show us that, for some of the affected population, pressure-lowering drops are beneficial."

Dr. Piltz-Seymour cautioned, however, that not all people with elevated eye pressure require treatment.

"While OHTS clearly showed a protective effect of treatment, it is important to remember that 90% of the participants in the observation (no eye drop) group did not develop glaucoma within the five-year study period.

When deciding when to treat, doctors and patients need to work together to evaluate the person's risk of developing glaucoma, their overall health and life expectancy, as well as the cost, inconvenience, and possible side effects of this treatment."

The study also showed that treatment of elevated eye pressure with eye drops had a very low incidence of side effects.

A third item that the study emphasized was the importance of corneal thickness measurement -- a procedure only recently recognized as important in evaluating a person for glaucoma. Researchers have identified that the accuracy of eye pressure readings can be influenced by the thickness of the cornea -- the front window of the eye. Thick corneas cause eye pressure readings to be higher than true pressure, while thin corneas cause pressure under-estimations. In the OHTS, eye with thinner corneas were found to be more at risk for the development of glaucoma, most likely because this group had higher eye pressures than were actually measured.

In addition to thin corneas, several other risk factors were found to be associated with the development of glaucoma in study participants. These included personal risk factors, such as older age and African descent, as well as ocular risk factors, such as higher eye pressure and certain characteristics in the anatomy of the optic nerve.

The Ocular Hypertension Treatment Study was sponsored by the National Eye Institute (NEI), one of the federal government's National Institutes of Health, the National Center on Minority Health and Health Disparities, Research to Prevent Blindness and Merck Research Laboratories.

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Editor's note:

Dr Piltz-Seymour does not have any financial interest in Merck Research Laboratories. Researchers were permitted to use an FDA-approved eye medication manufactured by any company. All eye drops were supplied by the study to the patient. Merck makes three medicated eye drops -- Timoptic, Trusopt; and Cosopt.