Quantitative optical coherence tomography reveals rod photoreceptor degeneration in early diabetic retinopathy

Purpose: This study is to test the feasibility of optical coherence tomography (OCT) detection of photoreceptor abnormality and to verify the photoreceptor abnormality is rod predominated in early DR . Methods: OCT images were acquired from normal eyes, diabetic eyes with no diabetic retinopathy (NoDR) and mild DR. Quantitative features, including length features quantifying band distances and reflectance intensity features among the external limiting membrane (ELM), inner segment ellipsoid (ISe), interdigitation zone (IZ) and retinal pigment epithelium (RPE) were determined. Comparative OCT analysis of central fovea, parafovea and perifovea were implemented to verify the photoreceptor abnormality is rod predominated in early DR. Results: Length abnormalities between the ISe and IZ also showed a decreasing trend among cohorts. Reflectance abnormalities of the ELM, IZ and ISe were observed between healthy, NoDR, and Mild DR eyes. The normalized ISe/RPE intensity ratio revealed a significant decreasing trend in the perifovea, but no detectable difference in central fovea. Conclusions: Quantitative OCT analysis consistently revealed outer retina, i.e., photoreceptor, changes in diabetic patients with NoDR and mild DR. Comparative analysis of central fovea, parafovea and perifovea confirmed the photoreceptor abnormality is rod predominated in early DR.