Aim: Prediabetic patients have generalized microvascular dysfunction, which leads to end-organ damage, just like diabetes. Therefore, prediabetes is not just a mild elevation in blood sugar, and early detection and prevention of possible complications should be the main goal. Color Doppler imaging (CDI) provides morphologic and vascular information on various diseases. The Resistive Index (RI) is a widely used measure of resistance to arterial flow and is calculated from the CDI. CDI evaluation of vessels in the retrobulbar region may be the first sign of micro- and macrovascular complications. Method: Consecutively, 55 prediabetic patients and 33 healthy subjects were recruited for the study. Prediabetic patients were divided into three groups according to their fasting and postprandial blood glucose values. The groups included an impaired fasting glucose (IFG) group (n = 15), an impaired glucose tolerance (IGT) group (n = 13), and an IFG+IGT group (n = 27). The RI of the ophthalmic artery, posterior ciliary artery, and central retinal artery were measured in all patients. Results: The orbital artery, central retinal artery, and posterior cerebral artery mean RI of prediabetic patients (0.76 ± 0.06, 0.69 ± 0.03, and 0.69 ± 0.04, respectively) were significantly higher than those of the healthy group (0.66 ± 0.04, 0.63 ± 0.04, and 0.66 ± 0.04, respectively; p < 0.001; Student’s t-test). The mean ophthalmic artery RI of the healthy, IFG, IGT, and IFG+IGT groups were 0.66 ± 0.39, 0.7 ± 0.27, 0.72 ± 0.29, and 0.82 ± 0.16, respectively, with a significant difference between the groups (p < 0.001, ANOVA). The mean central retinal artery RI of the healthy, IFG, IGT, and IFG+IGT groups were 0.63 ± 0.04, 0.66 ± 0.02, 0.7 ± 0.02, and 0.71 ± 0.02, respectively (p < 0.001, post-hoc Tukey). The mean posterior cerebral artery RI of the healthy, IFG, IGT, and IFG+IGT groups were 0.66 ± 0.04, 0.66 ± 0.04, 0.69 ± 0.03, and 0.71 ± 0.03, respectively, with a significant difference between the groups (p < 0.001 Fisher ANOVA). Conclusion: Increased RI may be the first sign of developing retinopathy, as well as the first sign of microangiopathies occurring simultaneously in the coronary, cerebral, and renal vessels. Precautions to be taken during the prediabetic stage can prevent many possible complications.