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Tear thinning time and topical anesthesia as assessed using the HIRCAL grid and the NCCA
K J Blades1, P J Murphy, S Patel
1Department of Vision Sciences, Glasgow Caledonian University, United Kingdom.
Background:
The literature contains conflicting reports of the effects of topical anesthetics on tear film stability, with some consensus that unpreserved topical anesthetics are less likely to reduce tear film stability than preserved preparations. This experiment investigated the effect of unpreserved 0.4% benoxinate hydrochloride on tear thinning time (TTT), in parallel with "real time" corneal sensitivity assessment.
Methods:
Tear film stability was assessed (HIRCAL grid) in parallel with real time assessment of the pharmacological activity (NCCA) of unpreserved 0.4% benoxinate hydrochloride in normal eyes.
Results:
The anesthetic used did not significantly affect tear film stability. This finding is in agreement with previous investigators.
Conclusions:
Unpreserved 0.4% benoxinate hydrochloride could be used to facilitate tear film stability assessment. The experimental protocol used could also be applied to investigate the temporal relationship between anesthesia and tear film stability with preserved topical anesthetics that have been found to decrease tear film stability.