A New Approach to Experimentally Determine Human Corneal Biomechanical Characteristics Using OCT Applied to an Anisotropic Finite Element Model

Abstract

 

Purpose:

 

Evaluate a new model to determine corneal elastic modules based on apical displacement under intraocular pressure(IOP)increase using OCT and loading this information to an anisotropic constitutive finite element model.

 

Methods:

 

Fresh human corneas with a 2-mm scleral ring and were used within 14 days of preservation. The corneas were mounted onto a modified Barron artificial anterior chamber with a predetermined reference landmark, adapted to a special holder with a positioning device. The system was monitored with an intraocular differential pressure transducer. Sequential cross-sectional OCT images of each cornea were taken in 4 meridians at each different IOP, ranging from zero to 90mmHg. Corneal displacement was measured in relation to the reference landmark to derive the stress-strain relationship between IOP and apical rise readings. The material parameters were fit, attempting to match the observed deformations, using a mathematical algorithm by inputting the loads into an anisotropic finite element model that accounts for the oriented structure of the collagen fibrils.

 

Results:

 

Images were successfully obtained in a reproducible manner and demonstrated the expected apical rise, significantly correlated to increasing of IOP (R2=0.990, p=<0,001). Displacement was observed for each IOP interval: 46, 98, 134, 170 and 221 µm at 10, 30, 50, 70 and 90mmHg, respectively. Maximum displacement occurred from zero to 90 mmHg was 221.21µm (p<0,001)

 

Conclusions:

 

This new model is useful to determine corneal biomechanical characteristics that are clinically relevant (apical rise) and may constitute an alternative method to tensile strength of corneal strips. Corneal apex axial displacement correlated well with rise in IOP.  

 

 

Keywords: computational modeling • cornea: basic science • imaging methods (CT, FA, ICG, MRI, OCT, RTA, SLO, ultrasound)