A Study of Consistency of Dexamethasone Responsiveness between Paired Bovine Eyes

Purpose: Glucocorticoid (GC) therapy can lead to elevated intraocular pressure (IOP) and GC-induced glaucoma. IOP elevation is also a major risk factor for the development and progression of primary open angle glaucoma (POAG). Glaucomatous and GC-induced IOP elevation is due to increased aqueous outflow resistance in the trabecular meshwork (TM). Because the pathological findings and clinical presentations of the two types of glaucoma are similar, GC-induce ocular hypertension is often used as a model to study POAG. Although the bovine eye perfusion culture model has been established, the consistency of paired bovine eyes to GC treatment has not been determined. Therefore, this study is to determine if Dexamethasone (DEX) changes IOP similarly in paired bovine eyes. Methods: Fresh bovine eyes were obtained from local abattoir, transferred to the lab and carefully dissected. The vitreous, uveal tract, retina, retinal pigment epithelium, and lens were removed. The remaining anterior segment, which contained the cornea, sclera, and TM, was mounted and sealed on a custom-made acrylic dish with an O-ring. Perfusion medium was infused by a syringe pump at a constant infusion rate of 5 μL/min. After IOP was stable, bovine eyes were perfused with medium containing 0.1% dexamethasone for 6-7 days. Bovine eyes with IOP elevation of more than 2.82mmHg was defined as a responder eye according to our published results. Results: Of the seven pairs of bovine eyes tested, one pair of eyes were DEX responders and the other six pairs were non-responders. The responder pair had IOP elevation of greater than 2.82mm Hg in both eyes. The other six pairs of non-responder eyes showed IOP change between -0.6 and 1.7 mm Hg. Conclusion: Our study showed that the DEX-responsiveness in paired bovine eyes are highly consistent. As suggested by early studies, it is very likely that induced IOP elevation and glaucoma are highly associated with genetic background. These results further validate the use of paired bovine eyes in glaucoma research. Due to the small samples size, further experiments are required. We will also try to determine possible genetic components such as the ratio between GC receptor isoforms GRα and GRβ in the TM cells.