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

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.

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.

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.

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.