A Cochrane review [Abstract] 1 included 26 studies with a total of 4979 subjects. Meta-analysis clearly demonstrated reduction of onset of visual field (VF) defects in treated ocular hypertension (OR 0.62, 95% CI 0.47 to 0.81; 10 studies, n=3648). No single drug showed a significant VF protection compared to placebo or untreated controls. The class of beta-blockers (including timolol) had positive but weak evidence for a beneficial effect in protecting against VF defects (OR 0.67, 95% CI 0.45 to 1.00; 8 studies, n=935). None of the studies continued to follow the patients under their original treatment once the first visual field defects had occurred.
A systematic review 2 including 5 studies with a total of 2320 subjects was abstracted in DARE. Pressure-lowering treatment was associated with a statistically significant preventive effect on visual field loss or deterioration of optic disc compared with no treatment (HR 0.56, 95% CI: 0.39 to 0.81; NNT 12, 95% CI: 9 to 29). The exclusion of one large study of the treatment of ocular hypertension, which dominated the results, led to no difference between the treatment and control. This suggested that the benefit of pressure-lowering treatment was only found in patients with an intraocular pressure of 24 mmHg or more. In open-angle glaucoma, pressure-lowering treatment was associated with a statistically significant preventive effect on visual field loss or deterioration of the optic disc compared with no treatment (HR 0.65, 95% CI: 0.49 to 0.87; NNT 7, 95% CI: 4 to 20). The subgroup analysis suggested a larger effect in patients with raised pressure and a reduced effect in patients with normal tension glaucoma.
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