Timolol treatment prevents or delays glaucomatous visual field loss in individuals with ocular hypertension: a five-year, randomized, double-masked, clinical trial

Abstract

A 5-year, randomized, double-masked, clinical trial was conducted to determine whether treatment with topical timolol maleate was effective in preventing or delaying the onset of glaucomatous visual field loss in subjects with ocular hypertension. Sixty-five individuals considered to be at moderate risk for developing open-angle glaucoma were recruited for the study. In each patient, one eye was chosen randomly to receive timolol twice-daily while the fellow eye received diluent (placebo). Timolol administration reduced IOP from baseline in the treated eyes over the course of the study by a mean +/- SD of 4.9 +/- 3.4 mm Hg. Timolol administration also produced a mean +/- SD contralateral reduction of IOP from baseline in the untreated fellow eyes of 2.9 +/- 3.1 mm Hg. The mean +/- SD difference in IOP between the treated and untreated eyes during the study was 2.3 +/- 2.6 mm Hg. Over the course of the study reproducible visual field loss developed in 4 timolol treated eyes and 10 placebo treated eyes (P = .039, McNemar test). Clinical progressive optic disc cupping was noted in four treated and eight untreated eyes (P = .11, McNemar test). In the 42 subjects who completed a minimum 4-year follow-up, baseline and final optic disc photographs were analyzed using a computer image analysis system to determine changes in the area of disc pallor. The mean +/- SD increase in optic disc pallor was 0.86% +/- 2.4% in the timolol treated eyes and 1.80% +/- 3.6% in the placebo treated eyes. This difference was statistically significant (P = .04, paired t-test). This study provides evidence that medical treatment prevents or delays the onset of glaucomatous visual field loss and optic disc damage in individuals with ocular hypertension. The magnitude of the protective effect of timolol was partially obscured by the contralateral reduction of IOP in the placebo treated fellow eyes.