Changes in intraocular pressure, horizontal pupil diameter and tear production during the use of topical 1% cyclopentolate in cats and rabbits

Background: Cyclopentolate is not commonly used as mydriatic drug in veterinary medicine because of limited data on the local and systemic effects in animals. Aim: To determine the effects of topical 1% cyclopentolate hydrochloride on intraocular pressure (IOP), horizontal pupil diameter (HPD) and tear production in the cat and rabbit’s eye during the first hour and up to 36 hours after treatment. Methods: One drop of 1% cyclopentolate hydrochloride was used in the left eye in 10 clinically and ophthalmologically healthy domestic cats and 10 rabbits. IOP and HPD were recorded every five minutes during the first hour, then every 2 hours during the following 12-hour period, and at 24 and 36 hours after application. STT was measured at 30 and 60 min after treatment, then in same time points as IOP and HPD. Rebound tonometer (TonoVet®) was used to assess IOP, Jameson calliper to measure HPD and Schirmer tear test (STT) to determine the tear production. Results: 1% cyclopentolate increased IOP in cats, reaching a maximum (28.1 ± 5.4 mmHg) at T50 and in rabbits at T25 (16,7 ± 1,3 mmHg). Maximal mydriasis in cats was observed at T40 and lasted 24-36 h, but in rabbits at T25, and returned to pre-treatment values at T10h - T12h. In cats, STT decreased in both eyes 30 min after treatment and remained lower throughout the 36h period. In rabbits STT decreased in the treated eye 30 min after treatment, but all following STT measurements returned to normal pre-treatment levels. Conclusion: Study showed novel data about the effects of 1% cyclopentolate to IOP, HPD, STT in cats and rabbits. Cyclopentolate in cats caused mydriasis 20 - 40 minutes after treatment by increasing IOP at the same time, pupil diameter reached pre-treatment values 24-36 h after treatment. In rabbit’s mydriasis accurred faster, 10-25 minutes after treatment without significant IOP increase and mydriasis lasted 10-12 hours. Significant STT decrease was recorded in cats, but more likely were connected to stress factors. This drug could be considered a therapeutical alternative in rabbit more than in cats