Abstract:

Glaucoma is a neurodegenerative disease identified by optic nerve damage and loss of retinal ganglionic cells. The aim of the study was to test the precise dose of trypsin to induce glaucoma in a rabbit model. Nine White New Zealand rabbits were randomly divided into three groups: Group one (G1) normal animals as control, group two (G2) the animals were injected with 0.2 ml of 0.04% trypsin and group three (G3) injected with 0.2 ml of 0.05% trypsin into posterior chamber of eye. A schiotz tonometer was used to measure intraocular pressure (IOP) before the injection, two days after injection and once a week until the end of the second week. At the end of the second week, the histology of the retina and optic nerve was studied. G3's intraocular pressure increased by 43.7%, while G2's intraocular pressure increased by 0.7% compared to G1. Retinal ganglionic cells (RGCs) decreased in G3 by 91.5% and G2 by 43.8% in comparison with G1. Optic nerve histology in G3 displayed decreased Schwann cell quantity with vacuolation and low orientation of nerve fibers compared with G1 and G2. Group three had the highest increase in IOP due to obstruction of drainage canal and preventing outflow of aqueous humor. This resulted in mechanical compression on the retina, ending with loss of RGC and degeneration of the optic nerve. The conclusion is that 0.2ml of 0.05% trypsin is the proper dose for the induction of glaucoma.

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