Effects of topical 0.5% tropicamide and 1% atropine on pupil diameter, intraocular pressure, and tear production, in healthy pet rabbits.

Objective: To evaluate the effects of topical application of 0.5% tropicamide and 1% atropine on pupil diameter (PD), intraocular pressure (IOP), and tear production (TP) in healthy pet rabbits.

Animals studied: Ten healthy client-owned rabbits.

Procedures: A prospective, randomized, blinded, crossover study was conducted. Each animal received one drop of 0.5% tropicamide or 1% atropine in a randomly selected eye. PD, IOP, and TP were evaluated before drug instillation and at 0.25 h, 0.5 h, 0.75 h, 1 h, 2 h, 4 h, 6 h, 8 h, 10 h, 12 h, 24 h, 36 h, 48 h, 60 h, and 72 h post-instillation. Data were analyzed using a paired two-sample repeated measures T-test with Bonferroni correction.

Results: In both tropicamide and atropine treated eyes, the mean PD significantly increased from 15 min until 12 h after treatment with a maximum PD at 45 min (+2.7 mm and + 2.4 mm respectively). Following tropicamide and atropine instillation, IOP increased significantly in treated eyes at 45 min (+2.9 mmHg) and 15 min (+5.2 mmHg) respectively, compared to untreated eyes. No significant effects were found on TP, in both tropicamide and atropine treated eyes at any time. No effects were observed in the untreated eyes on any of the parameters evaluated for both drugs.

Conclusions: Topical treatment with 0.5% tropicamide and 1% atropine induced mydriasis in healthy pet rabbits and could be considered as effective options when mydriatic/cycloplegic drugs are required.