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.
Clinical relevance: Our findings, to some extent, support the claims of the Ocular Hypertension Treatment Study, in which diabetes appeared to protect against the conversion to glaucoma. Targeted manipulation of neuronal energy metabolism may delay optic nerve degeneration and may represent a novel neuroprotective strategy for neurodegenerative diseases of the visual system such as glaucoma.