Optical coherence tomography and contrast sensitivity in early diabetic retinopathy

PURPOSE:This study used contrast sensitivity (CS) and optical coherence tomography (OCT) to assess the functional and structural alterations of the macula and the optic nerve head (ONH) in diabetic patients with no retinopathy and those with mild nonproliferative diabetic retinopathy (NPDR). MATERIALS AND METHODS:In this study, 40 eyes of 20 diabetic patients with no diabetic retinopathy (DR), 40 eyes of 20 diabetic patients with mild NPDR, and 36 eyes of 18 healthy individuals were examined. Best-corrected visual acuity (VA) and CS were performed using early treatment DR study charts and the Pelli-Robson chart, respectively. The macula and ONH were evaluated using OCT, which provided data on the entire retina, inner retinal layer, outer retinal layer, retinal nerve fiber layer (RNFL), and the macula zone-ellipsoid zone-retinal pigment epithelium layer. RESULTS:VA and CS were significantly different between the three groups (P < 0.001). The entire thickness of the retina and the internal thickness of the retina in the 3-6 mm subfields of the macular region, as well as the thickness of the ganglion cell layer + inner plexiform layer (GCL + IPL) and GCL + IPL + RNFLs, differed significantly across the groups (P < 0.013). CONCLUSION:In diabetic subjects with no retinopathy, the reduced thickness of the GCL + IPLs is possibly indicative of early neurodegenerative changes in the inner retina. Furthermore, in the diabetic groups, a decrease in CS was observed compared to the control group.