Purpose: Chronic hyperglycemia induces morphological and functional changes of the cornea. Corneal clarity is essential for visual function, and the measurement of corneal optical density (COD) might provide further information on diabetes mellitus (DM)-induced alterations.
Methods: COD of patients with DM and age-matched healthy subjects was measured using the Pentacam HR. Furthermore, central and thinnest corneal thickness and peripheral pachymetry of concentric circles around thinnest corneal thickness were investigated. In DM, information on disease duration, type, presence of diabetic retinopathy and maculopathy, and HbA1c value was recorded.
Results: In this study, 76 patients with DM and 65 healthy subjects were included. In patients with DM, the COD values of nearly all corneal layers and zones were reduced in comparison with healthy subjects (P < 0.05). Furthermore, the COD measurements were inversely correlated with the HbA1c value (total COD central layer: r = -0.424, P = 0.044) and stage of diabetic retinopathy (total COD: r = -0.271, P = 0.019). Diabetic patients with maculopathy revealed lower total COD values than patients without maculopathy (16.5 ± 5.6 vs. 21 ± 7.6, P = 0.031), and COD was lower in DM type 1 than in type 2 (16.1 ± 5.1 vs. 20.8 vs. 7.5, P = 0.035). In both groups, the COD values increased with age (patients with DM: r = 0.336, P = 0.003; healthy subjects: r = 0.679, P < 0.001) and decreased with peripheral corneal thickness increase.
Conclusions: In patients with DM, COD was significantly reduced in comparison with healthy subjects. These changes were associated to disease-specific factors and measurements of peripheral corneal thickness profiles.