To investigate the systemic parameters related to changes in the retinal microvasculature using optical coherence tomography angiography (OCTA) in diabetic patients without diabetic retinopathy.

We retrospectively reviewed the medical records of diabetic patients without diabetic retinopathy. All patients showed normal fundus on dilated fundus examinations. OCTA (DRI OCT Triton, Topcon Corporation, Tokyo, Japan) was performed on a 3 × 3 mm area centered at the fovea. The foveal avascular zone (FAZ) area and vascular density (VD) of the superficial and deep capillary plexus (SCP/DCP) were measured. Multiple regression analysis was conducted to evaluate the relationship between microvascular indexes on OCTA and systemic parameters including sex, age, duration of diabetes mellitus (DM), hemoglobin A1c (HbA1c), total cholesterol, presence of hypertension (HTN) and systolic and diastolic blood pressure (SBP/DBP).

A total of 35 eyes of 35 patients were included in this study. The mean age was 55.7 ± 11.6 years, the mean duration of DM was 52.4 ± 88.7 months and the mean HbA1c was 8.8 ± 2.3%. The FAZ area of the DCP increased significantly as the HbA1c level increased ( p < 0.001), but the other parameters, i.e., sex, age, duration of DM, total cholesterol, presence of HTN, SBP and DBP, did not exhibit significant relations in the DCP ( p = 0.727, 0.280, 0.385, 0.816, 0.206, 0.055 and 0.092, respectively). There were no significant relationships between systemic parameters and the FAZ area in the SCP ( p > 0.05). No systemic parameters exhibited significant relationships with VD in either the SCP or the DCP ( p > 0.05).

The FAZ area of the DCP detected via OCTA increased as the level of HbA1c increased, although the patients did not show diabetic retinopathy on dilated fundus examinations. Therefore, clinicians should consider this when screening diabetic patients for diabetic retinopathy.