Protection of retinal ganglion cells and the optic nerve during short-term hyperglycemia in experimental glaucoma

Objective: To evaluate the neuroprotective effect of short-term hyperglycemia on the retinal ganglion cell body and axon in a rat model of experimental glaucoma. Methods: Using a well-described limbal laser technique, unilateral ocular hypertension was induced in 2 groups (26 per group) of Sprague-Dawley rats. One group remained normoglycemic; the other was rendered hyperglycemic by means of an intraperitoneal injection of streptozocin. After 2 weeks of elevated intraocular pressure, axonal and retinal damage profiles were compared using several histological techniques. Immunohistochemical changes in the retina and optic nerve were also assessed. Results: We found convincing evidence of delayed axonal degeneration and retinal ganglion cell death in hyperglycemic rats. Axon loss was reduced by about 50% 2 weeks after induction of ocular hypertension. Survival of retinal ganglion cell perikarya increased to a similar extent in hyperglycemic rats. Conclusions: The optic nerve and retinal ganglion cells are partially protected by short-term hyperglycemia in this rat model of experimental glaucoma. Energy substrate availability may therefore play a role in glaucomatous optic neuropathy.Andreas Ebneter, Glyn Chidlow, John P. M. Wood, Robert J. Casso