Outer retina and choroid as potential imaging markers for evaluation of neural impairment in early type 2 diabetic patients

Purpose To quantify the presence of early structural alterations in the outer retinal layer and choroid among healthy subjects and diabetic patients with no or mild diabetic retinopathy, and to establish the correlation between the measured structural parameters and retinal sensitivity. Methods In total, 31 eyes from subjects with type 2 diabetes and 29 eyes from healthy subjects were enrolled. Optical coherence tomography was used to measure outer retina layers and choroid, while microperimetry was used to characterize the changes of visual function in a 6-mm diameter area at macula. Quantitative analysis of structural and functional changes was performed between groups and the structure-function correlations were determined. Results The thickness of myoid and ellipsoid zone, choroid and the mean retinal sensitivity were significantly smaller in diabetic group than that in controls (all P values < 0.05). Besides, thinner choroid and outer retina was associated with the decreased retinal sensitivity，especially in diabetic patients ( r = 0.377, P = 0.048; r = 0.401, P = 0.034; respectively). Final multiple regression models showed the outer retinal thickness (ORT) ( P = 0.033), choroidal thickness ( P = 0.003) and the interaction between ORT and choroidal thickness ( P = 0.001) were significant predictors to retinal sensitivity. Conclusions Thinning of choroid and outer retina were significantly correlated with reduced retinal sensitivity, which indicate outer retina and choroid might be potential imaging markers for evaluation of visual function related to neural impairment in type 2 diabetic patients without or in the early stage of diabetic retinopathy.