Detection of choroidal vascular features in diabetic patients without clinically visible diabetic retinopathy by optical coherence tomography angiography: A systemic review and meta-analysis.

Researchers have explored choroidal features in the eyes of diabetic patients without clinically visible diabetic retinopathy (DM-NoDR) employing optical coherence tomography angiography (OCTA); however, the results are controversial. We systematically searched PubMed, Embase, and Ovid databases for OCTA studies comparing choroidal parameters between DM-NoDR eyes and healthy controls or non-proliferative diabetic retinopathy (NPDR) eyes. Outcomes included choriocapillaris (CC) perfusion density (PD), flow area (FA), and flow deficits (FD). 36 studies were finally included in the quantitative meta-analysis, involving 1,908 DM-NoDR eyes, 792 NPDR eyes, and 1,391 healthy control eyes. DM-NoDR eyes had significantly lower CC PD in the foveal region (P=0.0005) and superior parafoveal region (P=0.003) than healthy control eyes, but no significant difference was found in other parafoveal subregions (P>0.05). DM-NoDR eyes were also associated with increased CC FD (P<0.00001) and decreased CC FA (P<0.0001) in whole OCTA images with a 3×3 mm² field of view (FOV). Compared with all-stage NPDR eyes, DM-NoDR eyes had higher CC PD in the foveal region (P<0.0001), parafoveal region (P<0.00001), and the whole OCTA images with a 6×6 mm² FOV (P<0.00001). Early choroidal microvascular changes may precede clinically visible DR and can be detected early using OCTA in DM-NoDR eyes.