Retinal Nerve Fiber Layer Thickness in Early-Stage Diabetic Retinopathy With Vitamin D Deficiency

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.