Comparison of the accommodation theories of Coleman and of Helmholtz by finite element simulations

Martin, H.; Guthoff, Rudolf; Terwee, T.; Schmitz, Klaus‐Peter

doi:10.1016/j.visres.2005.05.030

Cited by 41 publications

(36 citation statements)

References 9 publications

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“…The greater ciliary process movement than lens edge movement argues against the Coleman catenary theory (Coleman and Fish, 2001). If a pressure differential existed and was a primary force to induce accommodation, zonular tension would never be reduced because the lens would be pushed forward during accommodation by a pressure differential (Martin, Guthoff, Terwee and Schmitz, 2005).…”

Section: Discussionmentioning

confidence: 99%

Edinger-Westphal and pharmacologically stimulated accommodative refractive changes and lens and ciliary process movements in rhesus monkeys

Ostrin

Glasser

2007

Experimental Eye Research

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During accommodation, the refractive changes occur when the ciliary muscle contracts, releasing resting zonular tension and allowing the lens capsule to mold the lens into an accommodated form. This results in centripetal movement of the ciliary processes and lens edge. The goal of this study was to understand the relationship between accommodative refractive changes, ciliary process movements and lens edge movements during Edinger-Westphal (EW) and pharmacologically stimulated accommodation in adolescent rhesus monkeys. Experiments were performed on one eye each of three rhesus monkeys with permanent indwelling electrodes in the EW nucleus of the midbrain. EW stimulated accommodative refractive changes were measured with infrared photorefraction, and ciliary process and lens edge movements were measured with slit-lamp goniovideography on the temporal aspect of the eye. Images were recorded on the nasal aspect for one eye during EW stimulation. Image analysis was performed off-line at 30 Hz to determine refractive changes and ciliary body and lens edge movements during EW stimulated accommodation and after carbachol iontophoresis to determine drug induced accommodative movements. Maximum EW stimulated accommodation was 7.36 ± 0.49 D and pharmacologically stimulated accommodation was 14.44 ± 1.21 D. During EW stimulated accommodation, the ciliary processes and lens edge moved centripetally linearly by 0.030 ± 0.001 mm/D and 0.027 ± 0.001 mm/D, with a total movement of 0.219 ± 0.034 mm and 0.189 ± 0.023 mm, respectively. There was no significant nasal/temporal difference in ciliary process or lens edge movements. 30-40 minutes after pharmacologically stimulated accommodation, the ciliary processes moved centripetally a total of 0.411 ± 0.048 mm, or 0.030 ± 0.005 mm/D, and the lens edge moved centripetally 0.258 ± 0.014 mm, or 0.019 ± 0.003 mm/D. The peaks and valleys of the ciliary processes moved by similar amounts during both supramaximal EW and pharmacologically stimulated accommodation. In conclusion, this study shows, for the first time, that the ciliary processes and lens edge move centripetally, linearly with refraction during EW stimulated accommodation. During pharmacological stimulation, the ciliary processes move to a greater extent than the lens edge, confirming that in adolescent monkeys, lens movement limits the accommodative optical change in the eye.* corresponding author: aglasser@uh.edu.Publisher's Disclaimer: This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final citable form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. Accommodation is a dioptric change in power of the eye to focus on objects at different distances. In the unaccommod...

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Section: Discussionmentioning

confidence: 99%

Edinger-Westphal and pharmacologically stimulated accommodative refractive changes and lens and ciliary process movements in rhesus monkeys

Ostrin

Glasser

2007

Experimental Eye Research

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“…Ciliary muscles surrounding the lens and structural thin fibers called zonules that anchor the lens body to the ciliary muscles were thought to play a central role in the ability of the human eye to adjust for near or distant vision. Helmholtz' theory holds that when ciliary muscles relax, the zonules become subjected to tension, pulling the lens capsule along its equator and causing the lens body to flatten, thereby letting the eye see distant objects (Martin et al 2005). When the ciliary muscles contract, the zonules are released from tension, causing the lens body to become more curved, allowing the eye to focus on nearby objects (Alpern 1969;Fisher 1969;Burd et al 2002).…”

Section: Introductionmentioning

confidence: 99%

Accommodation of the human lens capsule using a finite element model based on nonlinear regionally anisotropic biomembranes

David

Pedrigi

Humphrey

2016

Computer Methods in Biomechanics and Biomedical Engineering

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Accommodation of the eyes, the mechanism that allows humans to focus their vision on near objects, naturally diminishes with age via presbyopia. People who have undergone cataract surgery, using current surgical methods and artificial lens implants, are also left without the ability to accommodate. The process of accommodation is generally well known; however the specific mechanical details have not been adequately explained due to difficulties and consequences of performing in vivo studies. Most studies have modeled the mechanics of accommodation under assumptions of a linearly elastic, isotropic, homogenous lens and lens capsule. Recent experimental and numerical studies showed that the lens capsule exhibits nonlinear elasticity and regional anisotropy. In this paper we present a numerical model of human accommodation using a membrane theory based finite element approach, incorporating recent findings on capsular properties. This study seeks to provide a novel perspective of the mechanics of accommodation. Such findings may prove significant in seeking biomedical solutions to restoring loss of visual power.

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“…Nevertheless, a majority of existing numerical models utilize this simplified and idealized description of accommodative apparatus, assuming that all sets of zonular fibers connect the lens to the ciliary processes in a single point with a resultant of the stretching forces lying in an equatorial plane, (e.g. Schachar and Bax 2001;Burd et al 2002;Martin et al 2005;Chien et al 2006).…”

Section: Introductionmentioning

confidence: 99%

Aspects of eye accommodation evaluated by finite elements

Ljubimova

Eriksson

Bauer

2007

Biomech Model Mechanobiol

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Axisymmetric nonlinear finite models of accommodation incorporating the posteriorly sloped force and vitreous effects have been studied by means of their effectiveness in mechanical and optical performances. All materials were assumed to be linearly elastic, vitreous and lens matrices were incompressible. The present model is subjected to certain indicated shortcomings, however, the behavior of the model is predictable, reasonable and favourably consistent with different published data, supporting the Helmholtz theory of accommodation.

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Comparison of the accommodation theories of Coleman and of Helmholtz by finite element simulations

Abstract: Physiologically relevant refractive power changes are obtained by a simulation in accordance with the Helmholtz theory. A simulation in accordance with the Coleman theory does not yield physiological values of refractive power change.

Cited by 41 publications

References 9 publications

Edinger-Westphal and pharmacologically stimulated accommodative refractive changes and lens and ciliary process movements in rhesus monkeys

Edinger-Westphal and pharmacologically stimulated accommodative refractive changes and lens and ciliary process movements in rhesus monkeys

Accommodation of the human lens capsule using a finite element model based on nonlinear regionally anisotropic biomembranes

Aspects of eye accommodation evaluated by finite elements

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