Corvis ST Assessment of Corneal Biomechanical Properties in Patients with Type 2 Diabetes Mellitus

Background and Objectives: Diabetes mellitus (DM) is associated with structural and biochemical changes in the cornea that may influence its biomechanical behavior. This study aimed to compare corneal biomechanical properties between healthy individuals and patients with type 2 DM. Materials and Methods: This observational cross-sectional study was conducted at a specialized ophthalmology center from September 2025 to April 2026 and included 115 eyes, which were divided into two groups: 60 healthy control eyes and 55 eyes of patients with DM type 2 (DM2 group). All subjects underwent a complete ophthalmological examination and corneal biomechanical screening using Corvis ST (Oculus Optikgeräte GmbH, Wetzlar, Germany). The study included participants aged 50–70 years, with central corneal thickness from 500 to 600 μm, and normal ocular findings. Exclusion criteria included a history of any previous corneal disease, uveitis, glaucoma, spherical refractive errors exceeding ±3.00 D, cylindrical refractive errors exceeding 3.00 D, prior ocular surgery, contact lens wear and systemic connective tissue diseases. Results: DM2 group was older than the control group (median age 63 years [IQR 57–68] vs. 56 years [IQR 54–59], p < 0.001). In unadjusted comparisons, deformation amplitude at highest concavity (DA HC) was higher in the DM2 group (1.05 [0.98–1.09] vs. 0.98 [0.91–1.06] mm, p = 0.002), as was integrated radius (IR) (8.00 [7.53–8.40] vs. 7.50 [6.60–8.60] mm−1, p = 0.032), whereas radius of curvature at highest concavity (RC HC) (7.41 [6.77–7.86] vs. 7.52 [7.10–8.04] mm, p = 0.038) and stiffness parameter at first applanation (SP-A1) (115.50 [102.18–128.40] vs. 122.50 [107.90–142.90] mmHg/mm, p = 0.023) were lower. After adjustment for age, gender, central corneal thickness and intraocular pressure, only DA HC remained independently associated with DM2 status (β = 0.033 mm, 95% CI 0.007–0.058; p = 0.012). Conclusions: Patients with type 2 DM exhibited a corneal biomechanical profile characterized by greater corneal deformability, reflected by higher DA HC and IR values and lower RC HC and SP-A1 values in unadjusted comparisons. Of these parameters, increased DA HC remained independently associated with DM2 after multivariable adjustment. These findings highlight the complexity of diabetes-related corneal biomechanical alterations and suggest that they may not uniformly manifest as increased corneal stiffness.