Lens shape change is influenced by zonular anchorage and stretching mechanism

This study investigates the influence of zonular anchorage position and loading mechanism on lens accommodation using finite element analysis. Axisymmetric models of the lens-zonule-ciliary body complex were developed, incorporating anterior, equatorial, and posterior zonular bundles. Four model variants were generated by varying anchorage position (near the pars plicata or pars plana) and loading mechanism (synchronous or asynchronous). Lens morphology, central optical power (COP) and zonular forces were analysed during simulated accommodation. The synchronous loading mechanism induced greater changes in posterior lens and nuclear radii of curvature and produced a wider range of accommodative change, while the asynchronous mechanism induced higher anterior surface steepening and peak central optical power but a smaller accommodative range. Zonular anchorage position slightly affected outcomes only in models with synchronous loading mechanism such that models with anchorage position near the pars plicata yielded greater changes in COP. A nonlinear relationship between central optical power and zonular force was consistently observed, suggesting an optimal range of zonular tension for maximizing lens performance. These findings indicate that zonular loading mechanism significantly influence lens shape and optical performance.