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

• Published in: Optics and lasers in engineering 2023-10, Vol.169, p.107747, Article 107747
• Main Authors: Gururani, Himanshu, Chittajallu, Sai Naga Sri Harsha, Manoharan, Ramji, Basu, Sayan, Chinthapenta, Viswanath
• Format: Article
• Language: English
• Subjects: Biomechanics; Corneal birefringence; Digital photoelasticity; Patient-specific; Rabbit cornea
• ISSN: 0143-8166; 1873-0302
• DOI: 10.1016/j.optlaseng.2023.107747

•The inter-individual variability of rabbit corneal birefringence is obtained experimentally.•The Ten-Step phase-shifting technique and Adaptive quality-guided phase unwrapping algorithm (AQGPU) is used to generate high-quality isoclinics and isochromatics of the rabbit cornea.•The birefringence features of phase-stepped images in both plane and circular polariscope configurations completely define the fibrillar structure of the cornea.•The rabbit corneal birefringence is presented as a benchmark for analyzing human corneal birefringence in-vitro conditions.•The translation of digital photoelasticity in clinical diagnostics for monitoring the fibrillar structure of the cornea is envisaged. 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.