Speaker
Description
The iris is a deformable circular diaphragm that regulates pupil size in response
to changes in illumination through the antagonistic actions of sphincter and
dilator muscles. While the phenomenological relationship between pupil size
and light intensity is well studied, the mechanical interplay between active
muscle contraction and passive iris tissue remains poorly understood. In this
study, we develop a finite element model of the human iris using an active strain
formulation to investigate the mechanics underlying pupil regulation under
physiological conditions. The iris is represented as a fiber-reinforced soft tissue,
with passive matrix behavior modeled as isotropic, nonlinear elastic and active
muscle contraction introduced via contractive strains along fiber directions.
Numerical simulations are performed using a dedicated finite element code. By
progressively including active and passive tissue components, we analyze how
tissue architecture affects pupil kinematics, stress distribution, and interaction
with supporting boundaries at the iris root. Results reveal a counterintuitive yet
significant role of passive tissues in shaping three-dimensional iris deformation
and moderating boundary reactions. This computational framework provides
a mechanically consistent basis for understanding iris biomechanics and can
support future studies extending to more complex physiological or pathological
conditions.