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Purpose: To evaluate retinal nerve fiber layer (RNFL) thickness in early-stage diabetic retinopathy (DR) patients with and without vitamin D deficiency (VDD)., Methods: This study compared 50 early-stage DR patients with VDD (group 1) and 50 early-stage DR patients without VDD (group 2). All patients were examined by the same ophthalmologist. Mean RNFL thickness was determined by optical coherence tomography (OCT) performed by the two independent ophthalmologists for all subjects. Vitamin D levels were measured by using a radioimmunoassay. Vitamin D deficiency was defined, in accordance with the general standards, as a 25-hydroxyvitamin D (25(OH)D) level lower than 20 ng/mL., Results: There were no significant differences between the groups in terms of age and sex distribution (P > 0.05). The mean serum 25(OH)D concentration of group 1 was significantly lower than that of group 2 (P < 0.001). The mean RNFL thickness of group 1 was significantly reduced compared to that of group 2 (P < 0.001). A significant relationship between the mean RNFL thickness and serum 25(OH)D concentrations was observed in group 1 (P < 0.001)., Conclusions: The results indicate that vitamin D functions as a neuroprotective component for optic nerves. Low serum 25(OH)D concentrations contribute to RNLF thinning in early-stage DR patients with VDD.

Purpose: To investigate the relationship between the erythrocyte membrane fatty acid components and diabetic retinopathy in patients with type 2 diabetes mellitus., Methods: The study was performed in 40 patients. Thirty of the 40 were type 2 diabetic patients classified into three groups according to Early Treatment Diabetic Retinopathy Study Group (ETDRS) criteria: 10 with mild-moderate nonproliferative retinopathy (group 1), 10 with moderate-severe nonproliferative retinopathy (group 2), and 10 with proliferative retinopathy (group 3). Ten age- and sex-matched healthy nondiabetic individuals were selected as controls. We examined the fatty acid composition of the erythrocyte membrane by a gas chromatographic method., Results: In patients with nonproliferative diabetic retinopathy, we found statistically significant decreases in palmitic and stearic acids, and statistically significant increases in oleic, linoleic, behenic, and lignoceric acids, while arachidic and arachidonic acids remained unchanged. Except for the increase in arachidic acid, the results were similar to those in the proliferative retinopathy patients., Conclusions: The fatty acid component of the erythrocyte membrane alters in type 2 diabetes mellitus. Prospective studies are needed to evaluate the relationship between the free-fatty acid composition of erythrocytes and diabetic retinopathy.