Materials and Methods: Eighty-nine eyes of 89 healthy volunteers were included. The patients younger than 51 years old were classified as group I and older than 64 years old were classified as group II. The patients were instilled a single drop of timolol maleat, brimonidine tartrate and latanoprost randomly. After evaluation for one drug a washout period of 1 week was allowed before second drug was evaluated. After baseline measurements, IOP measurements were repeated 2 hours after instillation of timolol and brimonidine drops and 12 hours after latanoprost drop.

Results: A single drop of each three drugs were found to be effective in IOP-lowering both in two groups. There were no statistically significant difference in IOP change between three drugs in group I, whereas there were statistically significant difference in group II. The differences between the effects of both timolol and brimonidine on two groups were statistically insignificant. The IOP reducing effect of latanoprost was 3.5±2.0 mmHg in group I and 2.5±2.4 mmHg in group II (p=0.007). There was a negative correlation between age and IOP reduction in latanoprost group (p=0.002), but no correlation was found in other two drugs.

Conclusion: Single doses of timolol, brimonidine and latanoprost have similar IOP-lowering effects in younger subjects. Timolol and brimonidine seemed to be more effective than latanoprost in reducing IOP in older cases. Keywords : Timolol, brimonidine, latanoprost, IOP-lowering effect, age, single dose