Background To investigate whether blood pressure and blood glucose levels affect retinal microvascular parameters, reflected by density within 300 mu m surrounding the avascular area of the fovea (FAZ), also called FD-300. Methods A case series study design was used to include patients with essential hypertension and/or type 2 diabetes who were hospitalized in the Department of Geriatrics, Beijing Tongren Hospital, from January 2023 to January 2024. FD-300 was measured via optical coherence tomography angiography. Multivariate linear regression analysis was used to adjust for confounding factors and then explore the influencing factors of FD-300. Results Patients were divided into four subgroups according to the quartile of FD-300. The median systolic blood pressure (SBP) levels of the four subgroups were 128 mmHg, 128 mmHg, 126 mmHg, and 121 mmHg, respectively, which were significantly different (p = 0.046). The median glycated hemoglobin (HbA1C) levels of the four subgroups were 6.50%, 6.40%, 6.50%, and 6.00%, respectively, which were significantly different (p = 0.012). Spearman correlation analysis revealed a significant negative correlation between SBP and FD-300 (r= -0.183, p < 0.05) and between HbA1c and FD-300 (r= -0.207, p < 0.05). Age, disease duration, cystatin C, and low-density lipoprotein cholesterol were also correlated with FD-300; they were confounding factors and were adjusted by multivariable linear regression. The results revealed that both SBP (beta=-0.07, p = 0.005) and HbA1c (beta=-1.00, p < 0.001) had significant effects on FD-300. Conclusion High blood pressure and glucose levels are risk factors for FD-300. Good control of blood pressure and glucose is of clinical importance for preventing retinal microangiopathy.