Discordance in Retinal and Choroidal Vascular Densities in Patients with Type 2 Diabetes Mellitus on Optical Coherence Tomography Angiography

Purpose. In the present study, the retinal and choroidal vascular densities (VDs) in type 2 diabetes mellitus (DM) patients were analyzed using optical coherence tomography angiography (OCTA). Methods. The study included 282 eyes of 152 patients with type 2 DM (114 without retinopathy, 79 nonproliferative diabetic retinopathy (NPDR), 48 severe NPDR, and 41 proliferative diabetic retinopathy (PDR) eyes). The superficial and deep retinal vessel, choriocapillaris, and choroidal VDs were measured using a binarization method on OCTA images. VDs were compared based on retinopathy severity. Correlations among densities were analyzed. Results. Retinal and choriocapillaris VDs were lower in PDR than in NPDR (all P<0.05). Correlation analysis showed significant positive correlations among densities of superficial and deep retinal vessels and choriocapillaris (all P<0.001). Choroidal VD showed a negative correlation with superficial and deep retinal vessels and choriocapillaris (all P<0.001). Retinal and choriocapillaris VDs showed a negative correlation with diabetic retinopathy (DR) grade (all P<0.001); however, the choroidal VD showed a weak positive correlation (P=0.030). Conclusion. Choroidal VD increased as retinal and choriocapillaris VDs decreased, indicating that the outer layer of the choroid is less affected by DR severity and VD of larger choroidal vessels may even be increased as a compensatory mechanism for decreased retinal and choriocapillaris VDs in type 2 DM patients.