Structural neurodegeneration correlates with early diabetic retinopathy

To examine differences in structural and functional neurodegenerative measurements between patients with no and early diabetic retinopathy (DR).

In this cross-sectional study, we examined 103 patients with type 2 diabetes mellitus. In 7-field fundus photographs acquired with Topcon TRC-NW6S, a single, certified grader determined the presence of DR according to the Early Treatment Diabetic Retinopathy Study (ETDRS) scale. Retinal neurodegeneration was evaluated by Topcon 3D OCT-2000 spectral domain optical coherence tomography (OCT) and by a RETI-scan multifocal electroretinography (mf-ERG) system in rings 1-6.

Median age and duration of diabetes were 63.6 and 10 years, respectively, and 46% were men. Median HbA1c was 50 mmol/mol (6.7%), and ETDRS levels were 10 (41.7%, n = 43), 20 (35.0%, n = 36), and 35 (23.3%, n = 24). The duration of diabetes increased with higher levels of DR (p = 0.04), but patients with different level of DR did not differ according to age, sex, blood pressure, HbA1c, and mf-ERG or OCT parameters. In a multiple logistic regression model, macular ganglion cell layer thickness was associated with the presence of DR (OR 1.73 per 5 μm increase, 95% CI 1.06-2.85, p = 0.03). Conversely, retinal nerve fibre layer thickness at optic disc was inversely related to DR (OR 0.69 per 5 μm increase, 95% CI 0.51-0.95, p = 0.02). There were no associations between DR and mf-ERG outcomes.

In patients with type 2 diabetes, structural neurogenic characteristics were associated with DR. If confirmed by larger prospective studies, these results may indicate that a complex neurovascular interaction is an early event in the pathogenesis of DR.