Background/Objectives: Impaired glucose metabolism may alter the corneal structure before overt diabetes develops. This study aimed to assess central corneal thickness (CCT) and central corneal epithelial thickness (CCET) using anterior segment optical coherence tomography (AS-OCT) in individuals with impaired glucose metabolism and to examine their relationships with anthropometric and biochemical parameters. Methods: This prospective cross-sectional study included 140 eyes from 70 participants: 20 healthy controls, 17 individuals with insulin resistance, and 33 with prediabetes. CCT and CCET were assessed using AS-OCT. Glucose metabolism was evaluated using a 2 h 75 g oral glucose tolerance test and glycated hemoglobin A1c (HbA1c). Anthropometric measurements, blood pressure, and biochemical parameters were also recorded. Results: The mean age of participants was 37.9 ± 12.3 years, and the mean HbA1c was 5.50 ± 0.38%. CCET was significantly higher in the prediabetes group than in the other groups (p < 0.01), whereas CCT did not differ significantly. CCET showed significant positive correlations with age, fasting plasma glucose, and HbA1c (all p < 0.05). In multivariable linear regression analyses, glycemic parameters remained independently associated with CCET after adjustment for age, sex, and BMI (p < 0.05). Conclusions: Impaired metabolic processes during prediabetes may influence corneal epithelial thickness. Our findings suggest that corneal parameters obtained by AS-OCT may provide supportive information by highlighting early corneal structural alterations associated with prediabetes. Accordingly, prediabetes detection should not be restricted to HbA1c and OGTT alone. However, longitudinal studies are required before any clinical application can be considered.