Suppression of corticosteroid-induced ocular hypertension in sheep by anecortave

Objective: To confirm the ocular hypotensive effects of anecortave acetate on an ovine model for steroid-induced ocular hypertension. Eyes of normal sheep exhibit a robust steroid-induced ocular hypertensive response. Recent observations in an uncontrolled, interventional case series indicated that anecortave elicited hypotensive effects when administered as a sub-Tenon depot in the eyes of a small sample of patients with glaucoma. Methods: Intraocular pressure (IOP) was monitored by Perkins applanation tonometry in 16 normal sheep receiving topically administered prednisolone acetate, 0.5%, in both eyes, 3 times daily, a protocol that doubled IOP within 12 days. Half of the sheep had received a unilateral sub-Tenon injection of anecortave in 1 eye prior to the initiation of the bilateral prednisolone instillations, while the 8 remaining sheep received the unilateral anecortave sub-Tenon depot after the IOP was maximally elevated by the prednisolone instillations. Results: In these 2 sets of experiments, the presence of the anecortave depot suppressed the steroid-induced IOP elevation and reverted the elevated IOP to baseline levels. Measurements of aqueous outflow facility indicated that eyes treated with prednisolone plus anecortave exhibited a 5.8-fold higher outflow facility than the fellow eyes solely exposed to prednisolone, indicating that anecortave prevented the increase in outflow resistance produced by the corticosteroid. Conclusion: Elucidation of the mechanisms of action of anecortave in animal models may prove relevant to the design of novel interventions for the management of primary open-angle glaucoma.