Purpose: We quantified retinal and choriocapillaris microvascular changes in healthy control eyes and different stages of diabetic retinopathy (DR) using optical coherence tomography angiography (OCTA).
Methods: This retrospective cross-sectional study included 137 eyes of 86 patients with different stages of DR and 44 eyes of 26 healthy age-matched controls. Participants were imaged with a commercial OCTA device (RTVue-XR Avanti). We analyzed the superficial (SCP) and deep (DCP) retinal capillary plexus, the full retina, and choriocapillaris for the following OCTA parameters: foveal avascular zone, vessel density, percent area of nonperfusion (PAN), and adjusted flow index (AFI). We adjusted for age, sex, and the correlation between eyes of the same study participant in our statistical models.
Results: All OCTA parameters showed a significant linear correlation with DR severity (P < 0.05) in the univariate models except for AFI measured in the SCP and these correlations remained significant after correcting for covariates. Compared to the other capillary layers, the AFI at the DCP decreased significantly with DR severity. When comparing individual disease severity groups as categories, eyes of subjects with diabetes without DR had significantly increased PAN and AFI in the SCP compared to healthy subjects (P < 0.05).
Conclusions: Retinal and choriocapillaris vascular nonperfusion in OCTA is correlated significantly with disease severity in eyes with DR. Higher flow in the SCP may be an early marker of diabetic microvascular changes before clinical signs of DR. The steep decline of blood flow in the DCP with increasing DR severity suggests that alterations at the DCP warrant further investigation.