Abstract
Purpose :
The mechanical properties of the sclera are relevant for the understanding of tissue remodelling and potential new treatments of myopia. Air pulse deformation imaging has been used to characterize the mechanical properties of the cornea in vivo, and has shown some potential for use in characterizing the sclera's mechanical properties. In this work, we studied the influence of parameters such as material preoperties, intraocular pressure (IOP), and tissue thickness on scleral deformation, using a parametrized finite element model of the porcine sclera.
Methods :
A three-dimensional finite element model of the porcine eye globe was created in ANSYS Mechanical. IOP was incorporated as an internal fluid volume. A one-term Ogden hyperelastic model was used to describe the non-linear elastic behavior of the tissue. A range of values were evaluated for each variable: thickness of .58 to 0.78 mm at site of air pulse loading, IOP of 15 to 30 mmHg, material model μ value of 0.01 to 0.1 MPa. Central displacement, central-peripheral deformation ratio, applanation time, and peak-to-peak distance were calculated from the deformed sclera. A multiple regression was done to quantify the influence of the independent variables.
Results :
Unlike results in the cornea, applanation and peak-to-peak distance do not appear to be suitable descriptors of deformation, as higher scleral rigidity produced small values in these parameters. Central displacement was found to be highly correlated to material properties (correlation coefficient R2=0.90), but thickness (R2=0.06) and IOP (R2=0.02) were poorly correlated. The influence of thickness and IOP was more pronounced for the upper range of deformation values (>1mm central displacement). At the lower range (>0.4mm), deformation is driven primarily by material coefficient.
Conclusions :
Porcine scleral deformation is influenced by elastic material properties, IOP, and thickness, with the former being the primary influence in the lower deformation range. Results suggest that air pulse deformation imaging could be used to estimate the elastic mechanical properties of the sclera in vivo.
This abstract was presented at the 2022 ARVO Annual Meeting, held in Denver, CO, May 1-4, 2022, and virtually.