Effects of two concentrations of topical tropicamide on the Schirmer tear test in clinically normal cats

Objectives The aim of this study was to evaluate the effect of topical tropicamide at two concentrations (0.5% and 1.0%) on the Schirmer tear test (STT) results in clinically normal cats. Methods Twenty-four adult domestic shorthair cats were randomly assigned to three groups. In all three groups, ophthalmic solutions were instilled in a randomly selected eye and the opposite eye served as the control. In groups 1, 2 and 3 one drop of 0.5% tropicamide, 1.0% tropicamide and distilled water was used, respectively. Tear production in both eyes was tested 30 and 60 mins after instillation in all three groups. Results Baseline mean +/- SEM STT values for the treated eyes in groups 1, 2 and 3 were 13.37 +/- 2.91 mm/min, 10.87 +/- 1.39 mm/min and 11.37 +/- 1.65 mm/min, respectively. Thirty minutes after the drug instillation in the treated eye, mean +/- SEM STT values in groups 1, 2 and 3 were 4.87 +/- 3.05 mm/min, 2.00 +/- 0.84 mm/min and 11.25 +/- 1.81 mm/min, respectively. The mean +/- SEM STT levels of the treated eye after 60 mins were 3.75 +/- 1.87 mm/min, 0.5 +/- 0.37 mm/min and 11.42 +/- 1.78 mm/min in groups 1, 2 and 3, respectively. Conclusions and relevance Use of 0.5% topical tropicamide, instead of 1.0% tropicamide, as a mydriatic agent, can be recommended in cats. Tear production measurement should be performed prior to the administration of tropicamide, regardless of the concentration of this drug.