Objective: To study diabetic retinopathy by the immunohistochemical and ultrastructural examination of changes in the retina in diabetic rats. Study Design: We examined the blood-retinal barrier and cell-to-cell connections in diabetic rats by immunohistochemistry and ultrastructural level. Twenty adult male Wistar rats were used in this study. The animals were divided into 2 groups. The control group was fed standard rat chow and drinking water for 8 weeks. Single-dose streptozotocin (55 mg/kg) was dissolved in sodium citrate buffer and administered via intraperitoneal injection to induce diabetes in the diabetes group. The diabetes and control groups were compared for glucose values. Results: The blood glucose concentration in diabetic rats was significantly increased (p < 0.05). Dilation of blood vessels, hemorrhage, and edema were observed in the nerve fibers and ganglion layer. An increase in vascular endothelial growth factor expression was confirmed by Western blot method. E-cadherin-positive cells in the immune junctions between cells in the diabetic retina were observed, weakly staining. Conclusion: Ultrastructural analysis of diabetic retinopathy showed that dysfunctionality of photoreceptor cells and vision loss are thought to occur due to mitochondrial degeneration. © Science Printers and Publishers, Inc.