Evaluation of photoreceptor integrity in diabetic retinopathy using high-resolution optical coherence tomography

BACKGROUND: The relative ellipsoid zone reflectivity (rEZR) is a promising imaging biomarker for photoreceptor integrity, but its variation across diabetic retinopathy (DR) stages remains unclear. This study investigates rEZR changes across different DR severities using high-resolution optical coherence tomography (OCT) imaging. METHODS: For this exploratory cross-sectional study, 64 eyes of 44 patients were included (17 eyes: no DR, 33 eyes: non-proliferative DR (NPDR), 14 eyes: proliferative DR (PDR)). Imaging was performed using high-resolution spectral-domain OCT (SPECTRALIS HighRes OCT, Heidelberg Engineering, axial resolution: 3 μm). rEZR (ratio between ellipsoid zone and external limiting membrane reflectivity) was measured at the foveola, within the Early Treatment Diabetic Retinopathy Study ETDRS grid (central 1 mm, inner ring, outer ring) and peripapillary. Linear mixed models assessed the association between rEZR, DR stage and visual acuity. RESULTS: In the outer macular ring, mean rEZR was significantly lower in PDR compared to no DR (p = 0.005) and NPDR (p = 0.045). In the total area, mean rEZR was significantly lower in PDR compared to no DR (p = 0.016) and NPDR (p = 0.032). Peripapillary mean rEZR was significantly lower in NPDR compared to no DR (p = 0.013) and in PDR compared to no DR (p = 0.033). No significant group differences were observed in the foveola, central 1 mm or inner macular ring. CONCLUSION: Our data suggest that more advanced stages of DR are associated with a decrease in photoreceptor integrity, with statistically significant group differences predominantly observed in the outer macular regions and peripapillary.