Chronic therapy of unilateral IOP elevation in rats

Purpose. We previously showed that single topical applications of antiglaucoma medications lower IOP in rats with unilateral sclerosis of the trabecular meshwork. This study is designed to determine if repeated application of such agents can produce chonic lowering of IOP in this model. Methods. Nine Brown Norway rats each received two injections of 1.75M hypertonic saline into the aqueous humor outflow pathways of one eye, one week apart. Following the second injection, animals received 10 μl of either 0.5% betaxolol, 0.5% apraclonidine or artificial tears in both eyes twice daily for 10 days. Awake IOP was measured frequently in masked fashion using the Tono Pen XL tonometer. Results: All animals receiving artificial tears developed definite elevations of IOP in the injected eye; over the entire 10 days, the mean ΔIOP (injected eye IOP minus the fellow eye IOP) was 9.46 ± 8.06 mm Hg (SD). In betaxolol treated animals, the mean ΔIOP was -0.89 ± 9.03 mm Hg. In the apraclonidine group, mean ΔIOP was 0.44 ± 5.77 mm Hg. Mean ΔIOP's of the betaxolol and apraclonidine treated eyes were not significantly different. However, mean ΔIOP for each was significantly lower than that seen in animals receiving artificial tears (p< 0.001). Conclusions. Repeated application of medications that suppress aqueous humor formation can chronically lower IOP in rat eyes with elevated IOP following sclerosis of the trabecular meshwork. This will allow us to determine if such treatment can prevent pressure-induced optic nerve damage in this model.