Effects of topical corticosteroid administration on intraocular pressure in normal and glaucomatous cats

Objective The objective of this study was to determine the effect of topical corticosteroid (CCS) therapy on intraocular pressure (IOP) in normal cats and cats with primary feline congenital glaucoma (FCG). Animals studied Five normal and 11 FCG cats were studied in two cohorts. Procedures IOP was measured by a single, masked observer, once daily, 3-5 days/week throughout the course of CCS treatment and for up to 11 days after treatment discontinuation. One eye per cat was randomly assigned for treatment twice daily with CCS; balanced salt solution (BSS) applied to the contralateral eye served as a control. Differences between eyes and between weeks of the study period were calculated for each cat. A positive response to CCS was defined as a consistent >15% or >25% higher IOP in the treated relative to control eye in normal and FCG cats, respectively. Results A total of 8 of 11 FCG cats responded to topical CCS after 1-5 weeks of treatment with an increase in IOP relative to the untreated eye (maximum IOP discrepancy of 56 mmHg). Two of five normal cats responded to topical CCS with an appreciable, but clinically unimportant increase in IOP in the treated eye (maximum IOP discrepancy of 6.4 mmHg). Conclusions Our data indicate that the incidence of steroid-induced IOP elevation in cats is lower than that of previously published feline studies. Cats with preexisting compromise in aqueous humor outflow may show a greater, clinically relevant response to topical CCS than normal cats.