This study examined potential therapeutic or preventive benefits of curcumin on the damage caused by hyperglycemia to the optic nerves of diabetic rats. Forty-two Wistar female albino rats were allocated to 7 groups at random, with 6 rats in each group. The rats of control group (Cont) were not subjected to any treatment. Corn oil (1ml/kg) was applied to Sham group (Sham) via gavage for 14 days. For the diabetes model, rats of four groups were given one dose of 50 mg/kg streptozotocin (STZ) intraperitoneally. The diabetic animals received gavage treatments of 30 mg/kg curcumin in corn oil for 14 days. Curcumin and STZ were applied simultaneously in the diabetes-curcumin 3 (DC3) group. Curcumin was given to the diabetes-curcumin 1 (DC1) group 7 days and to the diabetes-curcumin 2 (DC2) group 21 days after the diabetes model was created. The curcumin (Cur) group received just curcumin (30 mg/kg) in corn oil for 14 days). Histopathological analysis was performed on semi-thin (500 nm) sections. In thin (70 nm) sections, quantitative parameters of optic nerve were examined by stereological methods. Diabetes significantly reduced the number of myelinated axons compared to the control group (p<0.05). The DC2 group compared to the diabetes group had higher myelinated axons number (p<0.05). The effect of curcumin application on optic nerve of diabetic animals did not show any difference in other parameters. Qualitative analysis showed morphological changes in optic nerve and protective effect of curcumin in ultrastructural analysis, suggesting its potential therapeutic role against diabetic optic nerve damage. The electron microscopic analysis revealed that the morphology of the nerve fibres was preserved in the Cur group in comparison to the control group.