One-hour intraocular pressure response to timolol. Lack of correlation with long-term response

The initial topical administration of 1 drop of 0.25% timolol maleate in 25 nontreated ocular hypertensive patients resulted in a significant reduction of mean intraocular pressure one hour later, from a baseline of 28.1 +/- 5.3 (mean +/- SD) mm Hg to 18.5 +/- 4.5 mm Hg. Two patients (8%) failed to show at least a 10% decreases in IOP one hour after the initial administration. After three to four weeks of twice a day unilateral therapy with 0.25% timolol, mean IOP increased to 21.1 +/- 4.2 mm Hg. At this time seven patients (28%) failed to obtain a 10% decrease in IOP from topical timolol administration. Changing to 0.5% timolol for three to four weeks did not cause an additional significant lowering of IOP (20.4 +/- 3.5 mm Hg). At this time five patients (20%) had less than a 10% reduction in IOP. The one-hour response failed to predict future IOP nonresponsiveness.