Determination of tear break-up time reference values and ocular tolerance of tetracaine hydrochloride eyedops in healthy horses.

This research studies the effect of tetracaine hydrochloride eye drops on horses, primarily observing its impact on tear break-up time (TBUT) and overall ocular tolerance. The study found that while the drops caused no notable side effects, they did lower the TBUT.

Objective and Methodology

• The main objective of the research was to establish a method for measuring TBUT in horses, report any potential side effects of using THCl eye drops in healthy horses, especially its impact on tear film stability.
• The experiment was conducted in two parts. In Study 1, one drop of THCl (0.5 or 1%) was applied to the eye of 20 horses, divided into two groups. The eyes were then evaluated for side effects 2.5 and 5 minutes post-application.
• In Study 2, TBUT was measured in both eyes of two groups of 10 horses, before and after 2.5 and 5 minutes from instilling a drop of either 0.5 or 1% THCl.

Results

• None of the test subjects exhibited any ocular side effect after the application of the eye drops, indicating that THCl is well-tolerated in horses.
• However, it was noted that the TBUT decreased from the baseline after the application of the eye drops. This reduction was observed 5 minutes after applying a drop of 0.5% THCl and 2.5 minutes after applying a drop of 1% THCl.
• The basal TBUT was reported to be 8.3 ± 1.3 seconds.

Conclusion

• The researchers successfully developed a technique for measuring the TBUT in healthy horses and obtained a reference range for TBUT in this species.