Glycemic Status and its Relationship with Corneal Tomographic and Endothelial Parameters in Diabetes Mellitus

This study aims to compare corneal tomographic and endothelial parameters in diabetic patients with both controlled and uncontrolled glycemic status, as well as to investigate the relationships between corneal parameters, glycemic control, and the duration of diabetes. Conducted in a hospital setting, this cross-sectional study involved diabetic patients categorized into controlled and uncontrolled groups according to their HbA1c levels. Corneal tomography was executed utilizing Scheimpflug imaging, while endothelial evaluation was performed through non-contact specular microscopy. To maintain statistical independence, the right eye was predetermined for all inferential analyses. Between-group comparisons were carried out using suitable statistical tests, with effect sizes presented alongside p-values. Correlation and multivariable regression analyses were employed to assess the associations among corneal parameters, HbA1c levels, and the duration of diabetes. The findings revealed that patients with uncontrolled diabetes exhibited a significantly steeper flat keratometry (K1) in comparison to those with controlled glycemic status, with a moderate-to-large effect size, suggesting potential clinical significance. Conversely, other tomographic parameters such as steep keratometry, mean keratometry, central corneal thickness, anterior chamber depth, and corneal volume did not show significant differences between the groups and were associated with small effect sizes. Nevertheless, a greater dispersion of various tomographic parameters was descriptively noted in the uncontrolled diabetes cohort, indicating heightened structural variability. The density of endothelial cells was numerically elevated in the uncontrolled diabetes group; however, it did not achieve statistical significance and was associated with increased variability. Indices of endothelial morphology, such as the coefficient of variation and hexagonality, were similar across the groups. Correlation and multivariable regression analyses indicated no significant independent relationship between HbA1c and central corneal thickness or endothelial cell density after controlling for age, sex, and duration of diabetes. The magnitude of the observed regression coefficients fell below thresholds deemed clinically significant. Uncontrolled diabetes is linked to subtle changes in corneal curvature and increased structural variability, rather than consistent alterations in corneal thickness or endothelial parameters. These results imply heterogeneous, subclinical corneal involvement in diabetes and underscore the multifactorial nature of diabetes-related corneal changes. Larger longitudinal studies are necessary to elucidate their clinical implications.