Background: There is evidence that the ocular hypotensive effect of topical betablockers persists for at least 24 hours once beta-blockade has been achieved. In previous studies, the highest concentration of drug generally has been used for this purpose. Method: Home tonometry was performed with a self-tonometer by 14 patients to study the intraocular pressure (IOP) reduction of 0.5% timolol administered once daily in the morning or in the evening and of 0.25% timolol administered in the morning. The study was masked and included washout periods before and between the different regimens. At the end of each treatment period, the IOP was monitored five times daily for 3 days. Results: No significant difference in mean reduction of IOP was found between the morning instillation of once daily 0.5% timolol compared with evening instillation of 0.5% timolol. In addition, there was no statistically significant difference in the mean IOP reduction between once daily administration of 0.25% versus 0.5% timolol. Conclusions: This study indicates that a lower concentration of timolol maleate used once daily may achieve maximum IOP reduction. The time of the single administration appears not to make any difference.
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