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 nonproliferative 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 1908 DM-NoDR eyes, 792 NPDR eyes, and 1391 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.