Evaluating the Foveal Avascular Zone using Optical Coherence Tomography Angiography in patients with Diabetes: A Cross sectional study

Abstract

Background: Diabetic Retinopathy (DR) is a major microvascular complication of Diabetes Mellitus (DM) and a leading cause of blindness in working-age populations. The foveal avascular zone (FAZ) is an area of the retina devoid of blood vessels, which can enlarge due to diabetic macular ischemia. This study aimed to evaluate the FAZ in patients with varying stages of DR using Optical Coherence Tomography Angiography (OCTA). Methods: This cross-sectional study included diabetic patients and healthy controls from the Ophthalmology Clinic at Lenasia South Community Healthcare Clinic between February 2020 and February 2023. Inclusion criteria comprised adults over 18 years with a clear view of the fundus. FAZ area and perimeter were quantified using OCTA. Statistical analyses were conducted to compare FAZ metrics across groups and to assess correlations with HbA1c and renal function. Results: A total of 79 diabetic eyes and 16 control eyes were analyzed. Patients were categorized based on DR severity: no DR, mild DR, and moderate/severe DR. The mean FAZ area was significantly larger in diabetic patients compared to controls (p=0.021), with a notable increase in patients with moderate/severe DR. However, the differences in FAZ area between no DR and control groups were not statistically significant. FAZ perimeter measurements also showed significant differences (p=0.015), particularly between controls and moderate/severe DR. No significant correlations were found between FAZ metrics and HbA1c, urea, or creatinine levels. Conclusions: The findings suggest that FAZ enlargement is present even in the absence of clinically evident DR and correlates with the severity of diabetic retinopathy. These OCTA-derived metrics could serve as valuable biomarkers for early detection of diabetic macular ischemia. Further research with larger cohorts is warranted to elucidate the relationship between FAZ size and visual outcomes, including contrast sensitivity.