Objective: To determine whether once-daily, in the morning, topical application of the new ocular hypotensive prostaglandin analogue, latanoprost, yields nocturnal intraocular pressure (IOP) reduction similar to its diurnal IOP reducing efficacy.
Study design and patients: Placebo- controlled, randomized, and double-masked study on hospitalized patients with ocular hypertension or glaucoma. Patients in group 1 (n=9) were maintained on twice-daily applications of 0.5% timolol maleate. Patients in group 2 (n=10) terminated their timolol treatment 3 weeks before the beginning of the study. In both groups the test drug (0.005% latanoprost) and its vehicle (placebo) was applied by hospital staff every morning for 9 days.
Measurements: After 4 days of ambulatory treatment, patients were hospitalized, and IOP values were obtained in the supine and sitting positions with a handheld electronic tonometer (Tono-Pen XL, Bio-Rad, Glendale, Calif) and a Goldmann's applanation tonometer, covering every 2-hour interval, around the clock, but not more than at four time points per day during a 5-day period.
Results: The mean nocturnal IOPs (Goldmann's applanation tonometer) collected for 5 days were mean +/-SEM 17.9+/-0.6 vs 20.2+/-0.6 mm Hg and 16.8+/-0.3 vs 20.6+/-0.5 mm Hg for the study vs the control eyes in group 1 and group 2, respectively. These nocturnal IOP reductions were statistically significant (P<.001, two-tailed paired Student's t test). The differences between diurnal and nocturnal IOP reductions (handheld electronic or Goldmann's applanation tonometer) were minimal (>0.3 mm Hg) and statistically not significant (P>.31, two-tailed paired Student's t test).
Conclusion: Once-daily latanoprost treatment provides uniform circadian (around-the-clock) IOP reduction by itself, or in combination with timolol.