A Modelling Approach for Investigating Opto-Mechanical Relationship in the Human Eye Lens

Kehao Wang, Demetrios Venetsanos, Masato Hoshino, Kentaro Uesugi, Naoto Yagi, Barbara Pierscionek

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Abstract

OBJECTIVE: The human visual system alters its focus by a shape change of the eye lens. The extent to which the lens can adjust ocular refractive power is dependent to a significant extent on its material properties. Yet, the link between the optics and mechanics of the lens remains uncertain and relatively unexplored. This study aims to investigate this opto-mechanical link within the eye lens to gain insight into the processes of shape alteration and their respective decline with age.

METHODS: Finite Element models based on biological lenses were developed for five ages: 16, 35, 40, 57 and 62 years by correlating in vivo measurements of the longitudinal modulus using Brillouin scattering with in vitro X-ray interferometric measurements of refractive index and taking into account various directions of zonular force.

RESULTS: A model with radial cortical Young's moduli provides the same amount of refractive power with lesser change in thickness than a model with uniform cortical Young's modulus and shows uniform stress distributions with no discontinuities along the cortico-nucleus boundary. The direction of zonular angles can significantly influence curvature change regardless of the modulus distribution.

CONCLUSIONS: The present paper proposes a modelling approach, coupling optical and mechanical properties of human eye lens, which reveals the effect of parameter choice on model response.

SIGNIFICANCE: This advanced modelling approach, considering the important interplay between optical and mechanical properties, has potential for use in design of accommodating implant lenses and for investigating non-biological causes of pathological processes in the lens (e.g. cataract).

Original languageEnglish
Pages (from-to)(In-press)
JournalIEEE Transactions on Biomedical Engineering
Volume(In-press)
DOIs
Publication statusE-pub ahead of print - 5 Aug 2019

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Lenses
Optical properties
Elastic moduli
Brillouin scattering
Mechanical properties
Stress concentration
Optics
Refractive index
Materials properties
Mechanics
X rays

Bibliographical note

This work is licensed under a Creative Commons Attribution 4.0 License. For more information, see https://creativecommons.org/licenses/by/4.0/.

Keywords

  • Opto-Mechanical modelling
  • Finite Element Analysis
  • Human eye lens
  • Accommodation
  • Radial cortical Youngs moduli
  • Zonules

Cite this

A Modelling Approach for Investigating Opto-Mechanical Relationship in the Human Eye Lens. / Wang, Kehao; Venetsanos, Demetrios; Hoshino, Masato; Uesugi, Kentaro; Yagi, Naoto; Pierscionek, Barbara.

In: IEEE Transactions on Biomedical Engineering, Vol. (In-press), 05.08.2019, p. (In-press).

Research output: Contribution to journalArticle

Wang, Kehao ; Venetsanos, Demetrios ; Hoshino, Masato ; Uesugi, Kentaro ; Yagi, Naoto ; Pierscionek, Barbara. / A Modelling Approach for Investigating Opto-Mechanical Relationship in the Human Eye Lens. In: IEEE Transactions on Biomedical Engineering. 2019 ; Vol. (In-press). pp. (In-press).
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N2 - OBJECTIVE: The human visual system alters its focus by a shape change of the eye lens. The extent to which the lens can adjust ocular refractive power is dependent to a significant extent on its material properties. Yet, the link between the optics and mechanics of the lens remains uncertain and relatively unexplored. This study aims to investigate this opto-mechanical link within the eye lens to gain insight into the processes of shape alteration and their respective decline with age.METHODS: Finite Element models based on biological lenses were developed for five ages: 16, 35, 40, 57 and 62 years by correlating in vivo measurements of the longitudinal modulus using Brillouin scattering with in vitro X-ray interferometric measurements of refractive index and taking into account various directions of zonular force.RESULTS: A model with radial cortical Young's moduli provides the same amount of refractive power with lesser change in thickness than a model with uniform cortical Young's modulus and shows uniform stress distributions with no discontinuities along the cortico-nucleus boundary. The direction of zonular angles can significantly influence curvature change regardless of the modulus distribution.CONCLUSIONS: The present paper proposes a modelling approach, coupling optical and mechanical properties of human eye lens, which reveals the effect of parameter choice on model response.SIGNIFICANCE: This advanced modelling approach, considering the important interplay between optical and mechanical properties, has potential for use in design of accommodating implant lenses and for investigating non-biological causes of pathological processes in the lens (e.g. cataract).

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