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

Summary

Tetracaine hydrochloride is commonly used as a topical ocular anaesthetic in equine practice, yet its effects on tear film stability—a critical component of corneal health—had never been systematically characterised in horses. Monclin and colleagues established baseline tear break-up time (TBUT) reference values in healthy horses using a standardised protocol, then assessed whether tetracaine application caused any disruption to tear film integrity or local irritation signs. The research found that tetracaine hydrochloride did not significantly compromise TBUT or trigger adverse ocular responses in healthy equine eyes, providing reassurance about its safety profile in this species—a marked contrast to documented irritation in canine patients. These reference values and safety data are clinically valuable for practitioners performing ophthalmic examinations or procedures requiring topical anaesthesia, allowing differentiation between drug-induced tear film changes and pathological conditions affecting tear production or stability. Understanding the ocular tolerability of routine diagnostic agents strengthens confidence in their use whilst establishing benchmarks against which abnormal tear film function can be objectively measured.

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Key Findings

• •Study established reference values for tear break-up time (TBUT) in healthy horses using standardized technique
• •Tetracaine hydrochloride eyedrops were evaluated for ocular tolerance in equine subjects
• •Results provide baseline TBUT data for horses to enable detection of tear film abnormalities

Conditions Studied