Regional evaluation of corneal biomechanical properties based on inflation tests

Abstract

Corneal biomechanics are critical to both normal physiology and pathological conditions such as keratoconus (KC), yet existing measurement techniques fail to assess regional variations in material stiffness, limiting early diagnosis and therapeutic evaluation. This study focuses on evaluating the symmetry characteristics of bilateral corneal biomechanical properties based on a corneal inflation testing, while systematically analyzing the spatial distribution differences of biomechanical parameters in KC lesion regions and following corneal cross-linking (CXL) treatment. Thirty-six New Zealand white rabbits were divided into normal, KC-induced (via type I collagenase), and CXL-treated (riboflavin/ultraviolet light) groups. Four weeks post-intervention, corneal inflation tests were conducted, and the shear modulus (μ), the strain hardening index (α), and the tangent modulus (Et) in 25 different cornea regions were calculated. In the normal group, corneal material stiffness was similar in all 25 regions considered, with mirror symmetry and the highest Et in the upper temporal central region while the lowest in the lower temporal and peripheral nasal regions. Et of the central region reduced significantly in the KC group, while no statistical difference was found between the bilateral eyes in other 24 regions (all P > 0.05). Et enhanced after CXL, with the greatest increase in the central region and varying effects in other areas, correlating with preoperative properties. The analysis method provided a robust tool for capturing the regional biomechanical variations and derives morphology-independent biomechanical parameters, revealing localized stiffness losses in keratoconus and heterogeneous post-corneal cross linking stiffness enhancement.

Keywords: Biomechanical properties; Cornea; Corneal crosslinking; Inflation testing; Keratoconus.