A pooled-data analysis of three randomized, double-masked, six-month clinical studies comparing the intraocular pressure reducing effect of latanoprost and timolol

PURPOSE. TO compare the intraocular pressure (IOP) reduction by latanoprost and timolol, and to study factors of prognostic value for assessing this r eduction. METHODS. We analyzed 829 patients included in three phase III studies compa ring six months' treatment with 0.005% latanoprost once daily and 0.5% timo lol 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 afte rnoon assessments) by 7.7 mmHg (31%) and timolol by 6.5 mmHg (26%) after si x 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 th e initial morning IOP reduction obtained at two weeks. No such further decr ease in IOP was seen with timolol. Higher baseline diurnal IOP resulted in a larger diurnal reduction during treatment with both drugs (p<0.001). Diur nal 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 d iurnal IOP. The effect after two weeks was maintained for timolol while wit h latanoprost there was a further, significant IOP reduction from two weeks to six months. Baseline IOP was the only factor of clinical importance fou nd to be of prognostic value for assessing the IOP reduction.