The Relationship Between Corneal Stiffness Distribution and Tomography in Keratoconus Patients

To characterize the regional distribution of corneal stiffness in keratoconus (KC) and explore its relationship with tomographic parameters.

Prospective, cross-sectional observational study.

One hundred eleven eyes from 111 KC patients.

All eyes underwent Scheimpflug-based tomography and air-puff tonometry (Pentacam and Corvis). Stress-Strain Index (SSI) maps were generated to quantify overall and regional stiffness. Maximum, minimum, and mean SSI values, as well as regional values, were correlated with keratometric and pachymetric indices.

Regional SSI values and their correlations with keratometric and pachymetric parameters.

SSI maps showed non-uniform stiffness, with the lowest values predominantly in the inferior-temporal region. The mean SSI at the thinnest pachymetry point (Pmin; 0.68 ± 0.16) was higher than at the steepest keratometry point (Kmax; 0.63 ± 0.19; P = .036). In overall analyses, the strongest correlation was between SSI-map minimum and Pmin (R² = 0.51), while mean SSI correlated weakly with tomography (R² = 0.11-0.19). In regional analyses, SSI correlated most strongly with Kmax in the central region (R² = 0.74), followed by the midperipheral inferior (R² = 0.38) and temporal (R² = 0.23) regions. SSI correlations with Pmin were most evident in the central (R² = 0.52), paracentral inferior (R² = 0.45), and inferior-temporal (R² = 0.31) regions.

Biomechanical weakening in KC varies regionally. Strong correlations with disease severity occurred in the central and inferior-temporal regions - especially with Kmax and Pmin, highlighting the role of regional mechanical stiffness and collagen architecture in corneal deformation.