Steroid-Induced Ocular Hypertension in Normal Cattle

Objectives: To determine whether the bovine eye develops elevation of intraocular pressure (IOP) in response to topical corticosteroid use and to develop a reliable model of steroid-induced elevation of IOP in an animal. Methods: Intraocular pressure was monitored by Perkins applanation tonometry in a group of 12 cows receiving topically administered prednisolone acetate in 1 eye 3 times a day for a period of 49 days after the establishment of baseline IOP values. Perkins readings were converted to IOP in mm Hg using calibration curves derived from in vitro cannulation manometric experiments and validated with in vivo manometric measurements. Intraocular pressure was also monitored for 50 days after the discontinuation of corticosteroid therapy. Results: Intraocular pressure began to increase after 3 weeksoftreatmentin100%ofthecoweyesreceivingcorticosteroid and reached a peak 1 week later. Peak interocular IOP differences between the corticosteroidtreated eye and the fellow control eye reached up to 15 mm Hg and began to decline after the discontinuation oftreatmentbutremainedsignificantlyelevatedforaperiod of 3 more weeks. Conclusions: Bovine eyes exhibit a robust steroidinduced ocular hypertensive response, with 100% occurrence in this trial. The IOP elevation caused by corticosteroid slowly subsides after discontinuation of treatment. Clinical Relevance: The mechanisms of steroidinduced glaucoma may be related to those involved in primaryopen-angleglaucomaandcouldprovidetheclues toelucidatethepathogenesisofthelatter.Thehighprevalence of corticosteroid-induced elevation of IOP in the cow and the large amount of tissue available will permit studies on the mechanism of this phenomenon not previously possible. Arch Ophthalmol. 2004;122:1492-1497