SCLERAL RIGIDITY INFLUENCES CORNEAL BIOMECHANICS

Corneal biomechanics provides information on corneal tissue, which is of help to the clinician in the early diagnosis of different eye diseases, such as keratoconus. Nowadays, corneal biomechanics are gaining attention as potential disease biomarker. However, little is known about how the boundary structure, i.e., the sclera, might alter corneal biomechanical readings. The aim of the current work is to investigate the role of scleral stiffness on corneal maximum displacement during mechanical stimulation using a finite element model (FEM).

University of Zaragoza, Zaragoza, Spain

A three-dimensional finite element model including the cornea, the anterior sclera and the vitreous was implemented. These materials are defined as hyperelastic, following the parameters accessible from the literature, and applying a Holzapfel and Yeoh model for the cornea and the sclera, respectively. To achieve a realistic model, corneal fibers were taken into consideration. To mimic the mechanical stimulation of the cornea, an air-puff was simulated following the characteristics of commercially available tonometers. Intraocular pressure was fixed to 18 mmHg. Once the model was completed, scleral rigidity was modified from 0.4 MPa (soft sclera) to 1.6 MPa (hard sclera), and the corresponding maximum corneal deformation amplitude was evaluated.

Scleral stiffness greatly influenced the maximum corneal deformation amplitude. The relationship between scleral stiffness and the maximum corneal deformation amplitude can be defined by a linear equation. For a given cornea, the harder the sclera, the smaller the maximum deformation amplitude, and vice versa.

Biomechanical investigation of corneal tissue properties should take scleral stiffness into consideration because it modifies biomechanical corneal responses.