Optical coherence tomography angiography and microvascular changes in diabetic retinopathy: a systematic review.

To use optical coherence tomography angiography (OCTA) to evaluate foveal microvascular changes in diabetes by comparing the area of foveal avascular zone (FAZ) in healthy controls and patients with diabetes with no diabetic retinopathy (NDR) as well as different stages of diabetic retinopathy (DR). A systematic literature search was performed based on the population, intervention, comparison and outcome (PICO) strategy by two independent reviewers. The search was performed in PubMed, Embase and Cochrane Library, including keywords 'diabetes mellitus', 'DR' and 'OCTA'. Of 358 studies initially identified, 215 studies were screened after duplicate removal. Of these, we included 12 (nine cross-sectional and three retrospective) studies in this review. With the data at hand, it was not possible to perform a meta-analysis. The selected studies included patients with NDR (n = 8), non-proliferative diabetic retinopathy (NPDR, n = 8) and proliferative diabetic retinopathy (PDR, n = 6). Several of the studies provided information for more than one diabetic group. In general, there was a trend towards a larger area of FAZ in patients with diabetes. As compared to healthy controls, this was reported in patients with NDR (five of eight studies), NPDR (seven of eight studies) and PDR (six of six studies). Optical coherence tomography angiography (OCTA) is non-invasively able to identify foveal capillary non-perfusion as an early event in DR. In some studies, this has even been identified in patients without clinically identifiable microvascular lesions. Longitudinal studies would be needed to examine if OCTA-findings are able to predict long-term structural and functional outcome.