Clinical observation and experimental study on the role of choroid-to-retina volume ratio in diabetic retinopathy.

Aims: The retinal blood supply system reserve (RBSSR) reflects the vascular system's capacity to meet increased retinal metabolic demands and may be critical in the pathogenesis of diabetic retinopathy (DR). This study aimed to clinically measure and experimentally validate the choroid-to-retina volume ratio (CRVR) as an indicator of the RBSSR in DR.

Materials and methods: Diabetic patients were divided into NDR group (no apparent retinopathy, 134 eyes) and DR group (nonproliferative DR, 125 eyes) in the cross-sectional survey. Optical coherence tomography angiography (OCTA) 12 × 12 mm² fovea-centred scans were performed on subjects. Retinal and choroidal parameters were automatically measured, and the CRVR was analysed. Atropine eye drops were used for C57BL/6J mice modelling, and CRVR was examined by OCTA. Early DR mouse models were subsequently induced by streptozotocin, and fundus structural changes as well as retinal apoptosis were examined.

Results: The DR group exhibited significantly lower CRVR than the NDR group (all p < 0.05). Logistic regression analysis and area under the ROC curve (AUC) analysis indicate that low CRVR is a risk factor for DR, with all AUC values exceeding 0.70. Compared with controls, atropine increased the CRVR in mice. Additionally, eyes treated with atropine exhibited fewer punctate hyperfluorescent lesions, a tighter arrangement of the outer nuclear layer (ONL), and reduced apoptosis in the ONL and retinal pigment epithelium in early DR models.

Conclusions: The study supports the existence of the RBSSR and suggests that CRVR can serve as a potential indicator of RBSSR, highlighting its role in DR pathogenesis.