Five RCTs (n=2,320) evaluated ocular hypertension and 2 RCTs (n=400) evaluated open angle glaucoma.
Ocular hypertension.
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, 0.81; NNT 12, 95% CI: 9, 29). There was no evidence of statistical heterogeneity (P=0.185 and I-squared 35.4%).
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. Four of the 5 studies had high drop-out rates. The type of model used did not change the results obtained.
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, 0.87; NNT 7, 95% CI: 4, 20). There was no evidence of statistical heterogeneity (P=0.72). The subgroup analysis found a larger effect in patients with raised pressure and a reduced effect in patients with normal tension glaucoma. However, no significant difference was found in the comparison of these subgroups. The type of model used did not change the results obtained.