Title:Effect of Capsule Thickness and Material Properties on the Central
Optical Power of Natural Human Lens
Volume: 4
Issue: 1
Author(s): Reza Kakavand and Amin Komeili*
Affiliation:
- Department of Biomedical Engineering, University of Calgary, Alberta, Calgary, Canada
Keywords:
Human lens capsule, accommodation, strain, finite element analysis, sensitivity analysis, biconvex.
Abstract:
Background: A thin membrane capsule covers the eye lens and links the lens and the
applied forces by the ciliary muscles. The capsule converts the tension of the concentrated zonules
to distributed surface tractions over the cortex surface during the lens accommodation. The
gradual changes of the capsule geometry and material properties with age and its important role
in the design of intraocular lens implants were the motivation of extensive researches on
describing the capsule biomechanical behavior.
Aims: The present work aimed to study the lens accommodation response to different capsule
thicknesses and material properties at different ages.
Materials and Methods: A material and geometry parametric study was performed, drawing
some guidelines on the choice of lens capsule thickness and biaxial/uniaxial material parameters
and exploring the response sensitivity of the finite element model at different age groups.
Results: The 16-, 35- and 48-year-old lenses were considered for lens accommodation simulation.
The sensitivity of lens accommodation was studied at each age group by considering constant
thickness (cnst-t) and variable thickness (var-t) capsules and biaxial (Biax) and uniaxial
(Uniax) material characteristics tests. The lens was stretched through zonules, and corresponding
absolute changes in central optical power (COP) were measured.
Conclusion: After the stretch, the lens anterior and posterior curvatures increased, producing a
change in COP. The Biax models underestimated the ΔCOP compared to the Uniax models. The
16-year lens model was more sensitive to material properties than thickness variation, while
thickness variation was more relevant to the ΔCOP of the 35-year lens model. The 48-year model
had the least sensitivity to capsule thickness and material property variations.
