Functional effects of the spatial-varying lens mechanical properties in accommodation

Abstract

Lens biomechanical properties are critical for our eyes to accommodate. While it’s well understood that lens mechanical properties change with age, different experimental techniques have been used over the years, with varying results on how the lens modulus changes. In this study, we developed a spatial-varying elasticity model to characterize the overall elastic modulus of the lens and establish its effect on accommodation. First, to validate the model, ex vivo porcine lenses underwent compression testing using biopsy punches of different diameter to change the percentage of nucleus within samples. Importantly, we found that, indeed, changing nucleus/cortex spatial ratio produces dramatic (~7-fold) increase in overall sample modulus. Next, in vivo clinical measurements of the spatial-varying lens modulus were used to generate a simplified mechanical-optical model of accommodation. We defined a paraboloid lens with patient-derived modulus and geometry measurements, and a statics simulation and ray tracing analysis was performed through the deformed and undeformed lens. The resulting accommodation estimates agree with general accommodation expectations.