Identification of subject-specific fibrillar disposition in healthy rabbit cornea through birefringence analysis

Abstract

The cornea is an essential component in ocular biomechanics. The modifications in the collagen microstructure of the cornea affect its biomechanical behavior in various ocular conditions. Birefringence is an indicator of the microstructural changes in the cornea. The characterization of birefringence can benefit the patient-specific assessment of disease and surgically driven effects. According to the existing literature, optical birefringence of the cornea is best described as of biaxial nature. However, the biaxial model does not concur with the varying degree of birefringence observed amongst individuals. Using digital photoelasticity, the present study explores the applicability of birefringence of the healthy rabbit cornea as a benchmark model for human cornea. Eight freshly excised healthy rabbit corneas are imaged using the polariscope in the transmission mode. A fringe analysis is performed for each configuration of the polariscope to discern the collagen fiber distribution in the cornea. The birefringence of the rabbit corneas showed inter-corneal variability with varying degrees of biaxiality like the human corneas. Based on the fringe analysis, the fiber families in the cornea were identified in the form of geometric patterns distributed over the corneal surface and incorporated in the finite element model of the cornea. The present study envisages the utilization of birefringence-derived structural information to develop a reliable treatment design based on microstructural features of the cornea.