A quantitative geometric mechanics lens model: Insights into the mechanisms of accommodation and presbyopia

Reilly, Matthew A.

doi:10.1016/j.visres.2014.08.001

Cited by 20 publications

(16 citation statements)

References 67 publications

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“…Gross lens shape change caused by strain results microstructural level changes in all the regions of the lens that we examined. This provides critical information that will be useful in expanding current biomechanical models of lens shape changes (Reilly and Ravi, 2010;Reilly, 2014;Wang et al, 2017). Furthermore, the identification of a relationship between microstructure and tissue biomechanics supports the idea that age-dependent microstructural alterations, such as an increase in stiffness of cells or matrix (Starodubtseva, 2011;Lacolley et al, 2017), could have biomechanical consequences at the tissue level.…”

Section: Discussionsupporting

confidence: 53%

The effects of mechanical strain on mouse eye lens capsule and cellular microstructure

Parreno

Cheng

Nowak

et al. 2018

Preprint

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The understanding of multiscale load transfer within complex soft tissues is incomplete. The eye lens is ideal for multiscale tissue mechanics studies as its principal function is to fine focus light at different distances onto the retina via mechanical shape changes. The biomechanical function, resiliency, and intricate microstructure of the lens make it an excellent non-connective soft tissue model. We hypothesized that compressive strain applied onto whole lens tissue leads to deformation of specific microstructures and that this deformation is reversible following removal of load. For this examination, mouse lenses were compressed by sequential application of increasing load. Using confocal microscopy and quantitative image analysis, we determined that axial strain ≥10% reduces capsule thickness, expands epithelial cell area, and separates fiber cell tips at the anterior region of the lenses. At the equatorial region, strain ≥6% increases fiber cell widths. The effects of strain on lens epithelial cell area, capsule thickness, and equatorial fiber cell widths are reversible following the release of lenses from strain. However, although fiber cell tip separation following the removal of low loads is reversible, the separation becomes irreversible with application of higher loads. This irreversible separation between fiber cell tips leads to incomplete bulk lens resiliency. The lens is an accessible biomechanical model system that provides new insights on multiscale transfer of loads in soft tissues.

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Section: Discussionsupporting

confidence: 53%

The effects of mechanical strain on mouse eye lens capsule and cellular microstructure

Parreno

Cheng

Nowak

et al. 2018

Preprint

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“…4 The age-related changes in lens size and shape contribute to presbyopia and cataracts. [5][6][7][8] The driving force(s) for this continuous growth remain unknown, at least in part due to technical challenges with reproducing the lens' complex in vivo environment which includes biochemical and biomechanical influences. Flat-mount lens explants are frequently used to probe specific aspects of LEC behavior, but may not be appropriate for examining mechanobiological behavior due to altered cell morphology 9 and mechanical environment.…”

mentioning

confidence: 99%

Lens Stretching Modulates Lens Epithelial Cell Proliferation via YAP Regulation

Kumar

Chandler

Plageman

et al. 2019

Invest. Ophthalmol. Vis. Sci.

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PURPOSE. The continuous growth of the lens throughout life may contribute to the onset of age-related conditions in the lens (i.e., presbyopia and cataract). Volumetric growth is the result of continuous proliferation of lens epithelial cells (LECs). The driving factors controlling LEC proliferation are not well understood. This study tested the hypothesis that mechanical stretching modulates LEC proliferation. METHODS. Biomechanical regulation of LEC proliferation was investigated by culturing whole porcine lenses and connective tissues ex vivo under varying physiologically relevant stretching conditions using a bespoke lens stretching device. Additionally, some lenses were treated with a YAP function inhibitor to determine the Hippo signaling pathway's role in regulating lens growth. Resulting changes in LEC labeling index were analyzed using EdU incorporation and flow cytometry for each lens. RESULTS. LEC proliferation was found to be modulated by mechanical strain. Increasing both the magnitude of static stretching and the stretching frequency in cyclic stretching resulted in a proportional increase in the labeling indices of the LECs. Additionally, treatment with the YAP function inhibitor effectively eliminated this relationship. CONCLUSIONS. These data demonstrate that LEC proliferation is regulated in part, by the mechanotransduction of stresses induced in the lens capsule and that YAP plays an important role in mechanosensing. These results have important implications for understanding lens growth and morphogenesis. The model may also be used to identify and evaluate targets for modulating lens growth.

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“…Tscherning [19] suggested that the zonule fibres compressed the lens rather than relaxing it, and Schachar [20] has proposed that outward tension from the zonule fibres around the lens equator could flatten the outer zones of the lens, causing the centre to bulge, in the manner of a squeezed balloon. However, mechanical modelling, based on the most recent curvature data [21], has come down firmly in favour of the Helmholtz model, in which the curvature changes in the lens are the result of relaxation of the zonule.…”

Section: Helmholtz and Accommodationmentioning

confidence: 99%

Focusing by shape change in the lens of the eye: a commentary on Young (1801) ‘On the mechanism of the eye’

Land

2015

Phil. Trans. R. Soc. B

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In his Bakerian Lecture paper of 1801, Thomas Young provided the best account up to that time of the eye's optical system, including refraction by the cornea and the surfaces of the lens. He built a device, an optometer, for determining the eye's state of focus, making it possible to prescribe appropriate correction lenses. His main contribution, however, was to show that accommodation, the eye's focusing mechanism, was not the result of changes to the curvature of the cornea, nor to the length of the eye, but was due entirely to changes in the shape of the lens, which he described with impressive accuracy. He was wrong, however, in believing that the reason the lens bulges when focusing on near objects was because it behaved as a contracting muscle. Half a century later, Helmholtz showed that the lens bulges not by its own contraction, but when it is relaxed as a result of contraction of newly discovered circular muscles in the ciliary body. This commentary was written to celebrate the 350th anniversary of the journal Philosophical Transactions of the Royal Society.

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A quantitative geometric mechanics lens model: Insights into the mechanisms of accommodation and presbyopia

Cited by 20 publications

References 67 publications

The effects of mechanical strain on mouse eye lens capsule and cellular microstructure

The effects of mechanical strain on mouse eye lens capsule and cellular microstructure

Lens Stretching Modulates Lens Epithelial Cell Proliferation via YAP Regulation

Focusing by shape change in the lens of the eye: a commentary on Young (1801) ‘On the mechanism of the eye’

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