The Effect of Topical Verapamil in Q-Switched Nd:YAG Laser Induced Glaucoma Rabbits

ABSTRACT

To create an experimental glaucoma model in rabbit and to study the effect of elevated intraocular pressure (IOP) on rabbits ocular tissues, we treated trabecular meshwork of 7 adult pigmented rabbits with Q-switched NdYAG laser. And then we studied the IOP lowering effect of topical verapamil in experimental glaucoma model. The IOP and outflow facility were measured with an applanation pneumotonograph (Alcon, Texas). During sustained rap elevation, 50ul of 0.25% verapamil was instilled in one eye and normal saline in the fellow eye. The IOP was measured 1, 2, 4, 8 hours after instillation. The measurement was repeated twice at 2 weeks interval. After 5 weeks, the IOP increased from an average baseline IOP of 16.6mmHg to 25.51mmHg, an increase of 55.6%. The outflow facility was decreased from 0.21 microliter/min/mmHg to 0.09 microliter/min/mmHg. There were statistically significant reductions in IOP in both verapamil and placebo-treated eyes(p<0.05). The reduction was greater in verapamil-treated eyes than in placebo-treated eyes(p<0.05). Maximal reduction of IOP was observed 2 hours after single-drop of verapamil, with significant reduction of IOP up to 4 hours duration(p<0.05). During the observation period of this study, cupping of the optic nerve head developed. Histopathologic examination revealed extensive scarring of the anterior chamber angle structure. There are marked hyaline degeneration of retinal ganglion cells in temporal retina.