Stretch‐dependent changes in surface profiles of the human crystalline lens during accommodation: A finite element study. (March 2015)

• Record Type: Journal Article
• Authors: Pour, Hooman Mohammad; Kanapathipillai, Sangarapillai; Zarrabi, Khosrow; Manns, Fabrice; Ho, Arthur
• Is Part Of: Clinical & experimental optometry. Volume 98:Number 2(2015:Mar.)
• Page Start: 126
• Page End: 137
• Publication Date: 2015-03
• Subjects: Optometry -- Periodicals; Optometrists -- Services for -- Australia -- Periodicals; Optometry -- Periodicals; Optométrie -- Périodiques; 617.75
• DOI: 10.1111/cxo.12263
• Languages: English
• ISSNs: 0816-4622

Abstract

<abstract abstract-type="main"> <title> <x xml:space="preserve">Abstract</x> </title> <sec id="cxo12263-sec-0001" sec-type="section"> <title>Background</title> <p>A non‐linear isotropic finite element (FE) model of a 29‐year‐old human crystalline lens was constructed to study the effects of various geometrical parameters on lens accommodation.</p> </sec> <sec id="cxo12263-sec-0002" sec-type="section"> <title>Methods</title> <p>The model simulates dis‐accommodation by stretching of the lens and predicts the change in surface profiles of the lens capsule, cortex and nucleus at select states of stretching/accommodation. Multiple regression analysis (MRA) is used to develop a stretch‐dependent mathematical model relating the lens sagittal height to the radial position of the lens surface as a function of dis‐accommodative stretch. A load analysis is performed to compare the finite element results to empirical results from lens stretcher studies. Using the predicted geometrical changes, the optical response of the whole eye during accommodation was analysed by ray‐tracing.</p> </sec> <sec id="cxo12263-sec-0003" sec-type="section"> <title>Results</title> <p>Aspects of lens shape change relative to stretch were evaluated, including change in diameter, central thickness and accommodation. Maximum accommodation achieved was 10.29 D. From the multiple regression analysis, the stretch‐dependent mathematical model of the lens shape related lens curvatures as a function of lens ciliary stretch well (maximum mean‐square residual error 2.5 × 10<sup>‐3 </sup>μm, p < 0.001). The results are compared with those from <italic>in vitro</italic> studies.</p> </sec> <sec id="cxo12263-sec-0004" sec-type="section"> <title>Conclusions</title> <p>The finite element and ray‐tracing predictions are consistent with <italic>Ex Vivo</italic> Accommodation Simulator (EVAS) studies in terms of load and power change versus change in thickness. The mathematical stretch‐dependent model of accommodation presented may have utility in investigating lens behaviour at states other than the relaxed or fully accommodated states.</p> </sec> </abstract>