AIM: To evaluate the effect on intraocular pressure(IOP)of Latanoprost 0.005%(Lataprost, Sina Darou, Iran)applied every other day.

METHODS: Patients with well controlled open angle glaucoma were enrolled in the study. All patients had been given Latanoprost for at least 2 months with once daily dose at bed time at the first phase of the study. After recovery of 3 normal consecutive IOPs, the dosage was altered to once every other day at bed-time and they were closely monitored at week 1, 2, 4, 6, 8 and 12 within second phase of the study and IOPs were measured. As soon as an abnormally elevated IOP was encountered, patient was excluded from the study and the prior regimen was reestablished.

RESULTS:This study included 53 eyes of 53 patients(29 male, 24 female; age range 52-82 years)with open angle glaucoma. Twenty-seven patients suffered from primary open angle glaucoma and 26 patients had pseudoexfoliative glaucoma. After beginning the second phase of the study, a mild trend of increasing IOP was recordable. A corresponding trend was even detected in female and male patients separately. The P values at week 1, 2, 4, 6, 8 and 12 were 0.003, 0.001, 0.000, 0.000, 0.000 and 0.000 respectively. In the first 2 weeks after initiation of the 2^nd phase, 66% of cases have no change in IOPs, but thereafter, 69.8%, experienced increasing IOPs.

CONCLUSION: The present study shows the superiority of the conventional dosage of Latanoprost 0.005% in comparison with once every other day dose but at least in first few weeks, the IOPs are reasonably close to each other. Further studies with higher number of cases would widen the present findings.