Retinal sensitivity changes associated with diabetic neuropathy in the absence of diabetic retinopathy

Purpose: To explore any relationship between the markers of early retinal neuronal damage and peripheral diabetic neuropathy in subjects with no diabetic retinopathy (DR). Methods: A cross-sectional study in which type 2 diabetic subjects (n=743) without DR were studied. Visual functions including visual acuity, contrast sensitivity, colour vision, retinal sensitivity using microperimeter and retinal thicknesses by spectral domain optical coherence tomography were measured. Vibration perception thresholds of greater than or equal to 20 µV, measured by sensitometer using a biothesiometer probe, were defined as having peripheral diabetic neuropathy. Statistical analyses were performed using independent t-test, multivariate logistic regression and Pearson's correlation. Results: Of 743 subjects who had no DR, 24.9% had diabetic neuropathy. Independent comparisons among subjects who had diabetic neuropathy compared with those who did not showed statistically significant retinal nerve fibre layer thinning (p=0.01), reduced contrast sensitivity (p=0.0001), reduced retinal sensitivity (p=0.03), impaired colour vision (p=0.04) and reduced visual acuity (p=0.0001). Multivariate analysis showed significant association between the mean retinal sensitivity (measured using a microperimeter) and diabetic neuropathy (adjusted OR (95% CI): 0.76 (0.60 to 0.95), p=0.01). Conclusions: Significant association of neuroretinal dysfunction with the presence of diabetic neuropathy was noted among subjects with no DR.