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There are millions of people in the United States who have increased pressure in their eyes (intraocular pressure) without glaucoma. Often this condition is referred to as ocular hypertension.
Some of these people eventually develop glaucoma and loss of vision, whereas others lead their lives without developing the disease.
The Ocular Hypertension Treatment Study (OHTS) is funded by the National Eye Institute, a branch of the National Institutes of Health, to provide information to doctors and to patients about the proper management of people with this condition.
The OHTS had two major goals.
The first was to determine if early treatment of people who have increased intraocular pressure, with eye drops, would prevent them from developing glaucoma.
The second goal of OHTS was to determine which people are more likely to develop glaucoma, and therefore perhaps benefit from treatment; and which people with increased eye pressure are unlikely to develop glaucoma and therefore could probably be followed without treatment.
The OHTS began recruiting participants in 1994. We recruited 1,636 patients with ocular hypertension at 22 clinical centers around the United States. Twenty-five percent of the participants recruited were African-American because glaucoma is the leading cause of blindness in African-Americans.
The participants recruited were then randomly assigned either to be followed carefully without treatment or to receive eyedrop medication with the goal of reducing their intraocular pressure by 20 percent.
The participants were seen twice a year and had visual field studies performed; they had photographs of their optic discs taken once yearly. The diagnosis of glaucoma was made when the patient developed a reproducible visual field defect or a reproducible deterioration in the appearance of the optic disc. The optic disc is the visible portion of the nerve that connects the eye to the brain.
The patients entered into the Study were between 40 and 80 years old, had normal visual fields, normal optic discs, and had intraocular pressures between 24 and 32 mmHg. The patients randomly selected to be treated were given any commercially-available eyedrop medication that lowered intraocular pressure.
The results of OHTS proved that topical medication does reduce the incidence of glaucoma. After five years of following the patients recruited, we determined that eyedrop treatment reduced the development of glaucoma by more than 50 percent.
A detailed analysis was then performed to determine which patients were at greater risk for developing glaucoma. The predictive factors we found included increasing age, increasing intraocular pressure, decreased thickness of the cornea, and increased cup/disc ratio.
Using these factors, we were able to demonstrate that some ocular hypertensive patients are at very low risk of developing glaucoma, as low as one or two percent over five years, whereas other groups are at a much higher risk, as high as 25-35 percent over five years. Thus, some of these participants might benefit from receiving early treatment, whereas others appear to be at such low risk that it makes little sense to begin treatment.
The OHTS participants were studied very carefully to see if the medication was safe. We found little evidence of any group side effects, despite very careful survey of the patients using a variety of techniques.
African Americans in the Study appeared to fare worse than the other participants—more African Americans in the Observation Group developed glaucoma than did non-African Americans in the Observation Group, and more African-Americans in the Medication Group developed glaucoma than did non-African-Americans in the Medication Group. The poorer outcome in African Americans appears to be linked to the fact that African Americans have thinner central corneas and larger cup/disc ratios.
To this point, we believe the OHTS supports offering eyedrop treatment to ocular hypertensive people who are at moderate to high risk for developing glaucoma, taking into consideration the person’s age, medical status, life expectancy, and personal preference. The risk can be determined by looking at the patient’s age, intraocular pressure, corneal thickness, cup/disc ratio, and other clinical measures. If you have any questions about your situation, you should speak to your doctor for further information.
Article by Michael A. Kass, MD, Principal Investigator of the Ocular Hypertension Treatment Study (OHTS), a multicenter clinical trial conducted in 22 clinical centers in the United States. OHTS hopes to determine whether there is a penalty for delaying treatment in ocular hypertension.
Last reviewed on April 14, 2015
This article appeared in the May 2005 issue of Gleams.Subscribe