NEW YORK (Reuters Health) – Some patients with ocular hypertension are at low risk of progressing to open-angle glaucoma and don’t need treatment, research shows.

But for patients at high risk of glaucoma, early treatment helps protect against deteriorating vision, according to findings from the open-label extension of the Ocular Hypertension Treatment Study (OHTS).

“Phase 1 (of the OHTS) showed a proof of concept that early treatment is effective in preventing the onset of open angle glaucoma,” principal investigator Dr. Michael A. Kass told Reuters Health by email. “However, it did not tell us when people should be treated or whether all ocular hypertensive people should be treated.”

In the initial randomized phase conducted between 1994 and 2002, 812 patients received observation only and 806 used antihypertensive eye drops chosen by their eye doctor. Patients in the observation group started treatment only if glaucoma was diagnosed.

Baseline intraocular pressure was 24 to 32 mm Hg in at least one eye, but peripheral vision and optic discs (the portion of the optic nerve in the eye) were normal at trial start-up. The treatment target was a 20% decline to a pressure of 24 mm Hg or less.

In the open-label extension, which lasted until March 2009, all subjects were offered treatment. The median length of treatment was 5.5 years for patients first assigned to observation and 13 years for those in the intervention group.

As reported in the March Archives of Ophthalmology, at 13 years the cumulative proportions of subjects with glaucoma was 22% in the original observation group and 16% in the original medication group (p = 0.009). The median time to develop glaucoma was 6.0 and 8.7 years, respectively (p = 0.001).

But the surprising finding, Dr. Kass said, was “in the group with delayed treatment, where the protective effect of treatment occurred very rapidly.”

For example, in the randomized phase, the hazard ratio for developing glaucoma in the medication group compared with the observation group was 0.42. But in the extension phase, patients developed glaucoma at nearly identical rates: 12% in the original medication group and 11% in the original observation group (hazard ratio 1.06, p = 0.77).

The authors observed, however, that patients at lowest risk did not have a higher glaucoma risk if left untreated during the trial.

They estimated patients’ baseline 5-year risk of glaucoma based on a formula that took into account age, intra-ocular pressure, central corneal thickness, visual fields and optic discs.

In the lowest tertile of baseline risk, the 13-year cumulative rate of glaucoma was 8% in the observation group vs 7% in the medication group. Corresponding rates were 19% vs 14% in the second risk tertile, and 40% and 28% in the highest tertile.

The numbers needed to treat to prevent one case of primary open angle glaucoma were 11197, 16, and 7 for the first, second and third tertiles of risk, respectively.

“Most ocular hypertensive patients at low risk for developing glaucoma can be observed carefully without treatment,” Dr. Kass said.

“Conversely,” he added, “ocular hypertensive patients at high risk for developing glaucoma may benefit from early preventative treatment taking into consideration patient health status, life expectancy and personal preference.”

Reference:
Arch Ophthalmol 2010;128:276-287.

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