Changes of intraocular pressure in uveitic horses

Abstract

Objective: To describe changes of intraocular pressure (IOP) in horses affected by uveitis. Procedure: Study of medical records of 9 racehorses with unilateral uveitis (4 acute and 5 chronic) where IOPs were measured using a handheld applanation tonometer. Results: At first tonometry of the 9 horses, IOPs of the affected eyes (16.5 ± 5.1 mmHg) were significantly lower than those of the contralateral eyes (23.9 ± 4.7 mmHg). Two of the acute cases had lower IOPs in the affected eyes compared to the normal eyes, and changes in the IOP were monitored during treatment. Although both cases improved clinically, IOP recovered only in 1 case. In 4 of the chronically affected cases, uveitic eyes had developed phthisis bulbi and 3 of these eyes showed lowered IOP whereas the rest had IOP equivalent to the contralateral eye. The other chronic case, which had been affected by nonulcerative keratouveitis, had lowered IOP in the affected eye for 6 months, however, IOP difference between the both eyes got smaller. Conclusions: IOP can decrease with variable extent and duration in equine uveitis patients as well as in dogs [7]. However, IOP values of the affected equine eyes in this study were often higher than those of uveitic canine eyes [7]. Minor changes of IOP in uveitic eyes could be detected more accurately by tonometry than by observing or palpating the globes. IOP difference greater than 5 mmHg in each individual was considered to be a useful indicator in diagnosis of equine uveitis. Although further study is required, tonometry is a useful method to understand equine uveitis in detail, and should be included in complete ophthalmic examination especially in cases where the problem is longstanding and/or clinical progression is minor.