Steroid-Induced Ocular Hypertension in Normal Sheep

PURPOSE. To determine whether the ovine eye develops elevation of intraocular pressure (IOP) in response to corticosteroid applied topically. METHODS. IOP was monitored by Perkins applanation tonometry in a group of 18 sheep receiving topically administered 0.5% prednisolone acetate in one eye (experimental), three times daily, for a period of 3 or four 4 weeks after the establishment of baseline IOP values. Perkins readings were converted to actual mm Hg using a calibration curve derived from in vivo manometric measurements. IOP was monitored for an additional 1 to 3 weeks after discontinuation of corticosteroid treatment. RESULTS. Baseline IOP in normal sheep was 10.6 +/- 1.4 mm Hg (mean +/- SD; n = 36 eyes). The IOP of the experimental eyes began to increase after 1 week of prednisolone treatment in all sheep and reached a peak 1 week later (27.5 mm Hg experimental vs. 11.7 mm Hg fellow, control eye; P < 0.001). After the discontinuation of corticosteroid instillation, the IOP of the treated eyes declined to the baseline values over the course of 1 to 3 weeks. CONCLUSIONS. Ovine eyes exhibit a robust steroid-induced ocular hypertensive response, with 100% occurrence in this trial. The mechanisms of steroid-induced glaucoma may be related to those involved in primary open-angle glaucoma and could provide insight into primary open-angle and clues to its treatment. (Invest Ophthalmol Vis Sci. 2009;50:669-673) DOI:10.1167/iovs.08-2410