Presbyopic Correction as a Function of Scleral Expansion Using a 3-D Model of the Catenary Diaphragm

Abstract

Abstract: : Purpose: To demonstrate the effect of scleral expansion on anterior segment conformation and accommodative function using a simple physical model based on the caternary diaphragm theory Methods: A self-contained scaled 3-D model with a fixed videography system was used to approximate the disaccommodated and accommodated states with and without the presence of the force equivalent modification of a four point scleral expansion. Geometrically corrected images were segmented and edge detected; the model equivalent of the anterior lens surface was determined using a 5th degree polynomial and fits of general conics to segments of the axisymmetric surface. Results: Variations of lens curvature with induced deformation in the model shows good agreement with optical, ultrasound and MR data; and finite element analysis. Scleral expansion equivalent model realizations showed increased curvature range for an applied deformation. Conclusions: The physical model provides a good first order approximation for the major parameters of accommodation within the framework of the caternary diaphragm theory. Scleral expansion can be seen to effect accommodation without a need for alternate zonular theories.

Keywords: accommodation • aging • ciliary body