Ocular Effects of Topical 1% Cyclopentolate in New Zealand White Rabbits: A Controlled Evaluation of Intraocular Pressure, Pupil Size, and Tear Production.

Abstract

Objective: Mydriatic and cycloplegic agents are widely used in veterinary ophthalmology to enable posterior segment examination. This study evaluated the effects of topical 1% cyclopentolate on intraocular pressure (IOP), horizontal pupil diameter (HPD), and tear production measured by type 1 Schirmer tear test (STT1) in healthy albino rabbits.

Animals studied: Five healthy male New Zealand White rabbits were used for this study.

Procedures: A single drop of 1% cyclopentolate ophthalmic solution was instilled in the right eye, while the left eye received one drop of placebo and baseline IOP, HPD, and STT1 values were recorded (T0). Measurements of IOP, HPD, and STT1 were repeated in both eyes at 0.5, 1, 2, 4, 8, 12, 24, 48, and 72 h after administration.

Results: Topical 1% cyclopentolate produced a transient increase in IOP at 0.5 h (2.80 ± 2.49 mmHg, p = 0.008), followed by a temporary decrease at 2 and 4 h (p = 0.008 and p = 0.032, respectively), with no sustained differences thereafter. A significant mydriasis effect was observed in treated eyes within 0.5 h (1.2 ± 0.4 mm, p = 0.003), peaking at 1 h (1.4 ± 0.6 mm, p = 0.001) and returning to baseline by 8 h. STT1 values showed no significant change compared to the baseline values at any time, indicating no effect on tear production.

Conclusions: Topical 1% cyclopentolate causes transient alterations in IOP and HPD without affecting tear production in healthy rabbits, supporting its safety and diagnostic utility in veterinary ophthalmology.