Association Between Optical Coherence Tomography Angiography Findings and Inner Retinal Thickness in Diabetic Patients

OBJECTIVES: To investigate the association between optical coherence tomography angiography (OCTA) findings and inner retinal thickness (IRT) in diabetic patients. MATERIALS AND METHODS: This retrospective study included 23 eyes of 23 diabetic patients with retinopathy (group 1), 30 eyes of 30 diabetic patients without retinopathy (group 2), and 27 eyes of 27 non-diabetic age-matched controls (group 3). Foveal avascular zone (FAZ) area (mm(2)), average vessel density (%) in the parafoveal region, and average IRT in the parafoveal region (μm) were calculated using 6x6 mm OCTA images. Correlations between IRT and OCTA findings were analyzed. RESULTS: The mean FAZ area was 0.32±0.11 mm(2) in group 1, 0.29±0.08 mm(2) in group 2, and 0.22±0.09 mm(2) in group 3. There were statistically significant differences between groups 1 and 3 (p<0.001) and between groups 2 and 3 (p=0.001). Average IRT was 108.02±9.42 µm in group 1, 110.12±11.01 µm in group 2, and 114.41±5.21 µm in group 3, with statistically significant differences between groups 1 and 3 (p=0.003) and between groups 2 and 3 (p=0.014). In both group 1 and group 2, average IRT was correlated with FAZ area (r=-0.320 and -0.512, respectively). CONCLUSION: The inner retina is significantly thinner in diabetic patients with and without retinopathy compared to controls. Quantitative OCTA findings and IRT are correlated in diabetic patients, suggesting that both structures are compromised in patients with diabetes with or without retinopathy. Microvascular changes in FAZ detected by OCTA might precede neurodegenerative changes.