An Improved Monte Carlo Method for Quantitative Analysis of Transparency Degradation Caused by Corneal Edema.

Purpose: To address the impact of corneal edema on transparency, we proposed an improved Monte Carlo (MC) method that uses a cost-effective and easily applicable approach to extract fibril features. This method aims to enhance computational accuracy and elucidate microscopic mechanisms of corneal transparency.

Methods: Fresh ex vivo porcine corneas were immersed in deionized water to simulate various states of corneal edema. For each edema state, we carefully analyzed its transparency and fibrous conditions. The diameter and spatial distribution of corneal fibrils were measured using image recognition algorithms. An improved MC method, analyzing the multiple scattering of each incident light, was proposed to simulate the propagation of incident light in the cornea.

Results: Higher edema reduces transparency. After 10 hours of hydration, corneal water content increased by 7% and transparency decreased by over 30%. Cross-sectional observations indicated that the radius increases from the original 15.1 nm to 16.8 nm, the fibril-to-base material area ratio decreases from the initial 15% to roughly 7%, and the minimum gap between fibrils expanded by 35%. The proposed MC method provides more accurate transparency estimates compared to the direct summation of field theory.

Conclusions: Corneal transparency decreases as a result of multiple factors, including fibril and cornea thickening, variations in the refractive index, and changes in the fibril distribution.

Translational Relevance: The MC method is cost-effective, easily applicable, and accurate in predicting the transparency of corneas with varying water contents. Moreover, this method intuitively demonstrates the scattering of light during the propagation process.