Effect of topical ophthalmic dorzolamide(2%)-timolol(0.5%) solution and ointment on intraocular pressure in normal horses.

The study investigates the impact of dorzolamide(2%)-timolol(0.5%) solution and ointment on intraocular pressure in horses, finding that both applications have similar effects.

Methods

• The study employed a randomized, masked prospective design.
• Eighteen clinically normal horses were utilized and were further divided into two equal groups.
• In each horse, one eye was chosen for the treatment. One group received 0.2 mL of dorzolamide(2%)-timolol(0.5%) solution, and the other was treated with 0.2 g of dorzolamide(2%)-timolol(0.5%) ointment. Both treatments were applied every 12 hours for 5 days.
• The contralateral eye of horses in both groups remained untouched, serving as a control.
• To measure intraocular pressure (IOP), rebound tonometry was performed every 6 hours, beginning 2 days before and ending 2 days after the treatment period.

Results

• The reduction of IOP in eyes treated with either the solution or the ointment was statistically significant, averaging at 13%.
• The eyes that were left untreated in both groups also experienced a lesser, yet statistically significant, decline in IOP.
• Notably, IOP levels did not return to the baseline within 48 hours after the last treatment was applied.

Conclusion

• The study concludes that both the commercially available solution and compounded ointment formulations of dorzolamide(2%)-timolol(0.5%) exhibited similar effects on reducing the intraocular pressure in clinically normal horses.
• The sustained reduction in IOP, even after cessation of the treatment, might indicate that the drug effect is prolonged or that the horses have acclimated to the tonometry process.