AIM: To study optic nerve lesions, changes in blood flow to the optic nerve, and permeability of micro blood vessels and histopathology in diabetic rats. METHODS: Male Wistar rats (n=20) were randomly divided into control and diabetic groups. The diabetic model was prepared by a single injection of streptozotocin (50mg/kg) into the caudal vein. Three months later, laser Doppler perfusion imaging was used to observe the changes in blood flow to the optic nerve. Each rat was injected with 15g/L Evans blue (5μL/g). The permeability of microvessels in diabetic optic nerves was measured by spectrophotometry. Optic nerves were observed by light and transmission electron microscopy. RESULTS: Diabetic rats had atrophic optic nerve fibers with neurite swelling, loss of myelin, and a greater-than-normal proliferation of astrocytes, occurring within 3 months of induction of diabetes. Blood flow to the optic nerve was lower in diabetic rats than in controls. Microvessel permeability in diabetic rats increased 2.03-fold compared to controls. CONCLUSION: Diabetic rats develop significant pathological changes in the optic nerve, reduced blood flow to the optic nerve and increase microvessel permeability.