Increased axial resolution OCT improves structure-function correlation of the disorganization of the retinal inner layers in diabetic retinal disease

This study aimed to determine whether optical coherence tomography (OCT) with enhanced axial resolution improves structural characterization of the disorganization of the retinal inner layers (DRIL) in diabetic retinal disease (DRD) and its association with functional and vascular alterations. In this prospective cross-sectional study, 55 diabetic patients, 27 with DRIL (age: 57.1 ± 14.6 years) and 28 eyes without DRIL with diabetes mellitus (DM) type I/II (age: 58.2 ± 13.0 years), were examined with conventional spectral-domain OCT (SD-OCT), High-Resolution (High-Res) OCT, OCT angiography (OCTA), and microperimetry. DRIL areas were significantly smaller on High-Res OCT compared to SD-OCT (mean ± standard deviation, 0.3 ± 0.3 vs. 1.3 ± 1.2 mm², p < 0.001). OCTA analyses demonstrated persistent group differences in superficial and deep vessel density and FAZ circularity between DRIL eyes and eyes without DRIL, even after adjustment for clinical diabetic retinopathy severity score (DRSS, all p < 0.05). Within DRIL eyes, intra-eye analysis revealed a stepwise reduction in retinal sensitivity from areas with DRIL detected on both OCT modalities (Zone I: 13.1 ± 1.3 dB) to areas with DRIL only on SD-OCT (Zone II: 20.6 ± 0.8 dB) and to unaffected retina (Zone III: 23.1 ± 0.7 dB, overall p < 0.001). OCT with enhanced axial resolution refines DRIL detection, aligning more precisely with localized functional and vascular impairment.