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St. Louis—The main lesson to be learned from the Ocular Hypertension Treatment Study (OHTS) is that not every patient with ocular hypertension needs to be treated, according to Michael A. Kass, MD, a professor in the department of ophthalmology and visual sciences at Washington University in St. Louis, and chairman of the groundbreaking large-scale study.
St. Louis-The main lesson to be learned from the Ocular Hypertension Treatment Study (OHTS) is that not every patient with ocular hypertension needs to be treated, according to Michael A. Kass, MD, a professor in the department of ophthalmology and visual sciences at Washington University in St. Louis, and chairman of the groundbreaking large-scale study.
"The clinician should consider offering treatment to selected patients with ocular hypertension who are thought to be at moderate or high risk for developing glaucoma, taking into consideration a variety of factors, including the patient's age, medical status, life expectancy, likely treatment benefit, and personal preference," Dr. Kass said in a symposium on primary eye-care management problems at the American Academy of Ophthalmology annual meeting.
"We also believe that measuring central corneal thickness is useful in most patients who have ocular hypertension or glaucoma," he added.
Dr. Kass explained that OHTS was designed to help the comprehensive ophthalmologist decide what to do with a patient who has elevated IOP but no detectable damage.
"If you're a comprehensive ophthalmologist and you see 40 patients in a day, I'm going to make a guesstimate that at least one or two of them probably fall into this category, so this is not a rare phenomenon," he said.
A 22-site, multicenter prospective study, OHTS had two major goals.
"The first was once and for all to answer this question of whether early treatment can delay or prevent the onset of glaucoma. This question has been kicking around for 50 years, so it was time to answer it," Dr. Kass said. "The second goal was to identify certain patient features that would predict which patients with ocular hypertension are at high risk and which ones are at low risk for developing glaucoma."
OHTS enrolled 1,636 individuals between the ages of 40 and 80. Patients with IOP between 24 and 32 mm Hg in one eye and between 21 and 32 mm Hg in the other eye were randomly assigned to either observation or medication. Participants in the medication group could receive any commercially available eye drop to lower pressure. The goal was a reduction in pressure of 20% and a pressure of less than 24 mm Hg.
Patients were seen twice a year. Humphrey 30-2 visual field analysis was performed at each visit, and stereophotographs were taken once a year. A reproducible field abnormality was defined as three abnormal fields in a row. A reproducible disc deterioration was defined as a change detected on two sets of photographs in a row.
The baseline pressure in both groups was about 25 mm Hg. Mean IOP reduction in the medication group was 22.5% ±The baseline 9.9% and in the observation group, 4.0% ±11.6%. The difference between the groups was about 20% over the course of the study.
One of the main findings from the study was that treatment with a topical ocular hypotensive medication reduced the risk of progression to POAG. At 60 months, the cumulative probability of developing POAG was 9.5% in the observation group and 4.4% in the medication group.
"This difference was statistically significant [p < 0.0001] whether you considered visual field changes alone, optic disc changes alone, or both of them together," Dr. Kass said.
Most of the first glaucomatous changes occurred in the optic disc, and more people had disc changes than had field changes. However, some patients had field changes without an apparent disc change, and others had both changes simultaneously.
African-American subgroup Dr. Kass also discussed findings among the subgroup of 408 African-Americans enrolled in the study. Treatment was effective at delaying or preventing the onset of glaucoma in African-Americans; the rate of progression to POAG was 16.1% in the observation group and 8.4% in the medication group.