Effect of topical 1% cyclopentolate hydrochloride on tear production, pupil size, and intraocular pressure in healthy Beagles

© 2015 American College of Veterinary Ophthalmologists Objective: The objective of the study was to evaluate the effect of topical 1% cyclopentolate hydrochloride (CH) on tear production (TP), pupil size (PS), and intraocular pressure (IOP) in dogs. Animal studied: Fifteen healthy beagle dogs from the UAB research-teaching colony. Procedure: Dogs without ocular diseases were included. Each animal received one drop of 1% CH ophthalmic solution in a randomly selected eye. TP, PS, and IOP were evaluated by means of STT-1, static pupillometry, and rebound tonometry, respectively. Evaluations were performed before drug instillation and at 0.5, 1, 2, 4, 8, 12, 24, 30, 36, 48, 54, 60, 72, 84, and 96 h postinstillation. Examinations took place in a room with fixed light intensity (40–55 lux). Statistical analysis was performed by means of generalized estimating equations for the effect on STT-1, pupil size, and IOP over time. Results: After unilateral application of 1% CH, significant pupillary dilation started at 30 min, reached its maximum at 12 h, and returned to pre-instillation size after 72 h. No significant effects were found on TP or IOP, at any time. No effects were observed in the untreated eye on any of the parameters evaluated. Conclusion: Cyclopentolate hydrochloride could be considered a therapeutic alternative when use of a cycloplegic drug is needed and effects on tear production and IOP are unwanted.