Regional Differences in Young's Modulus of the Porcine Lens Capsule

The ocular lens capsule is a biomechanically specialized basement membrane essential for lens function, yet its regional micromechanical properties remain incompletely characterized.

We employed atomic force microscopy (AFM)-based force spectroscopy to map the stiffness of young porcine anterior and posterior lens capsule samples under physiologically hydrated conditions. A refined dissection protocol was used to preserve native curvature and hydration, with the anterior and posterior regions isolated via selective capsular puncture. Force-indentation measurements were performed using calibrated silicon cantilevers and analyzed with the Johnson-Kendall-Roberts (JKR) model to extract local Young's modulus.

Results from over 12,000 force curves revealed that the anterior capsule exhibited significantly higher stiffness (mean 67.9 kPa, standard deviation 40.1 kPa) than the posterior (mean 54.1 kPa, standard deviation 25.2 kPa; p < 0.0001), with a wider range of stiffness values. AFM topography confirmed comparable surface morphology, ruling out roughness as a confounding factor.

These findings highlight the functional specialization of the lens capsule and the utility of AFM for high-resolution biomechanical characterization. These measurement techniques will be applied to human lens capsules to elucidate age-related changes in capsule properties pertaining to presbyopia, inform surgical strategies, lens capsule modeling, and the design of accommodative intraocular lenses.