Anatomical changes in the retinal capillary plexuses assessed by optical coherence tomography angiography in diabetic patients

Purpose: To assess anatomical changes in the retinal superficial capillary (SCP) and deep capillary (PCP) plexuses, as well as choriocapillary (CC) in patients with diabetes mellitus (DM) without diabetic retinopathy (DR), and in DM patients with mild and moderate DR without diabetic macular edema (DME) using optical coherence tomography angiography (OCTA). Methods: Ninety eyes were included, 34 patients with long‐term DM (more than 10 years) but without DR signs, and 54 patients with mild or moderate DR (levels 35 and 43 on the ETDRS scale) without DME. All participants underwent a complete ophthalmic examination including best corrected visual acuity (BCVA) and OCTA examination using deep‐range imaging with the DRI‐Triton SS‐OCT. Results: The mean age was 63.82 ± 8.56 years and 63.00 ± 13.21 years in long‐term DM without DR and with DR, respectively. In patients with long‐term DM without DR, foveal avascular zone (FAZ) abnormalities were seen in both SCP and DCP (55% and 5%), and microaneurysms (MAs) were present in SCP and DCP (35% and 47.5%). Loss of perfusion was detected in SCP and DCP (30% and 47.5%), and ischemia was observed in SCP, DCP and CC (60%, 37.5% and 10%). In patients with mild or moderate DR without DME, OCTA also detected morphological abnormalities such as FAZ changes and MAs (79.6% and 81.11%), loss of perfusion (83.3% and 64.2%), and ischemia (66.67%, 81.1% and 18.5%) in SCP, DCP and CC respectively. Microvascular tortuosity and intraretinal microvascular anomalies (IRMAs) were detected in 48.1% and 46.3% in SCP vs 22.6% and 20.8% in DCP, respectively. Conclusions: Patients with long‐term DM without DR present morphological changes measured with OCTA, such as MAs in both retinal plexuses. The changes in the FAZ are more evident in the SCP due to the capillary anastomosis. Capillary dropout can be found in both plexuses. Patients with DR show more evident changes that include MAs, loss of perfusion and ischemia and other vascular abnormalities.