Purpose: To compare the intraocular pressure (IOP) reduction by latanoprost and timolol, and to study factors of prognostic value for assessing this reduction.
Methods: We analyzed 829 patients included in three phase 111 studies comparing six months' treatment with 0.005% latanoprost once daily and 0.5% timolol twice daily in patients with open-angle glaucoma or ocular hypertension. Analysis of covariance controlled for differences in baseline IOP and sex was used to assess the IOP reduction.
Results: Latanoprost reduced diurnal IOP (average of morning, noon and afternoon assessments) by 7.7 mmHg (31%) and timolol by 6.5 mmHg (26%) after six months of treatment. Thus the diurnal IOP was reduced 1.2 mmHg (18%) more with latanoprost than with timolol (p<0.001). Latanoprost-treated patients showed a further decrease in morning IOP of 0.7 mmHg (9%, p<0.001) from the initial morning IOP reduction obtained at two weeks. No such further decrease in IOP was seen with timolol. Higher baseline diurnal IOP resulted in a larger diurnal reduction during treatment with both drugs (p<0.001). Diurnal IOP in women was reduced 0.7 mmHg (11%) less than males with both drugs (p<0.001).
Conclusions: Latanoprost was more effective than timolol in reducing mean diurnal IOP. The effect after two weeks was maintained for timolol while with latanoprost there was a further, significant IOP reduction from two weeks to six months. Baseline IOP was the only factor of clinical importance found to be of prognostic value for assessing the IOP reduction.