Analysis of Foveal Microvascular Abnormalities in Diabetic Retinopathy Using Optical Coherence Tomography Angiography with Projection Artifact Removal.

Purpose: To analyze foveal microvascular abnormalities in different stages of diabetic retinopathy (DR) using optical coherence tomography angiography (OCTA) with projection artifact removal (PAR).

Methods: We analyzed 93 eyes of 59 patients with diabetes-31 with no DR (no DR), 34 with mild to moderate nonproliferative DR (mild DR), and 28 with severe nonproliferative DR to proliferative DR (severe DR)-and 31 age-matched healthy controls. Sections measuring 3 × 3 mm centered on the fovea were obtained using OCTA. The area, perimeter, and acircularity index (AI) of the foveal avascular zone (FAZ), vessel density within a 300 m wide region of the FAZ (FD-300), and parafoveal vessel density in the superficial capillary plexus (SCP) and deep capillary plexus (DCP) were calculated using novel built-in software with PAR.

Results: There was no statistically significant difference in the FAZ area (=0.162). There was a statistically significant difference in the FAZ perimeter (=0.010) and the AI ( < 0.001) between the four groups. There was a correlation between the AI and the increasing severity of DR (=0.010). Statistically significant decreases of vessel density in the FD-300, SCP, and DCP were observed (all < 0.001). There was a difference in parafoveal vessel density in the DCP between the healthy control eyes and the eyes with diabetes without DR (=0.027). There was a significant correlation between vessel density and increasing severity of DR ( < 0.001).

Conclusion: Compared with the FAZ area, AI allows a more helpful quantitative assessment of the changes in the FAZ. Vessel density determined using OCTA with PAR might be a useful parameter indicating the progression of DR. Parafoveal vessel density in the DCP after PAR might be a potential early biomarker of DR before appearance of clinically evident retinopathy and needs further investigation.