Medical interventions for primary open angle glaucoma and ocular hypertension

Ocular hypertension (OHT) is a condition with raised intraocular pressure (IOP) without visual field changes or discernible pathology of the optic nerve head. Ocular hypertension with IOP above 21 mmHg untreated is a major risk factor for development of primary open angle glaucoma, which is progressive nerve fibre loss and damage to the optic disc so that the visual field develops characteristic defects. Topical medications are given to reduce the IOP as a way of preventing the onset or progression of damage and associated visual field loss. These medications may have local and systemic side effects that may be severe enough for the treatment to be stopped and include local irritation, drowsiness, shortage of breath and cardiovascular side effects, particularly in the elderly. The results of this review support the current practice of topical medication to lower IOP and clearly demonstrate a visual field protective effect. The review authors identified a total of 26 controlled trials that randomised 4979 people with OHT or open angle glaucoma to receive topical medication or a placebo, another topical medication or no treatment for at least a year. Meta-analysis of 10 trials testing different topical medications against placebo or untreated controls showed reduced incidence of glaucomatous visual field defects with treatment for people with OHT. The odds ratio (OR) was 0.62 (range 0.5 to 0.8). The class of beta-blockers (including timolol) had positive but weak evidence for a beneficial effect in protecting against visual field defects (OR 0.7, range 0.5 to 1.0). No single drug showed significant visual field protection in OHT with the evidence available. Medications included beta-blockers, dorzolamide, brimonidine, pilocarpine and epinephrine. From the reports, the majority of trials were of low methodological quality. Local and systemic side effects leading to treatment being stopped were often poorly reported and did not appear to differ between treatment groups. Drop-outs due to side effects occurred with similar frequency in people treated with beta-blocker or placebo and appeared to be less with timolol compared to brimonidine, in three trials.