Hyperelastic modelling of the crystalline lens: Accommodation and presbyopia
Purpose: The modification of the mechanical properties of the human crystalline lens with age can be a major cause of presbyopia. Since these properties cannot be measured in vivo, numerical simulation can be used to estimate them. We propose an inverse method to determine age-dependent change in th...
| Main Authors: | , , |
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| Format: | Article |
| Language: | English |
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Elsevier
2012-07-01
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| Series: | Journal of Optometry |
| Subjects: | |
| Online Access: | http://www.sciencedirect.com/science/article/pii/S188842961200060X |
| _version_ | 1819151544449236992 |
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| author | Elena Lanchares Rafael Navarro Begoña Calvo |
| author_facet | Elena Lanchares Rafael Navarro Begoña Calvo |
| author_sort | Elena Lanchares |
| collection | DOAJ |
| description | Purpose: The modification of the mechanical properties of the human crystalline lens with age can be a major cause of presbyopia. Since these properties cannot be measured in vivo, numerical simulation can be used to estimate them. We propose an inverse method to determine age-dependent change in the material properties of the tissues composing the human crystalline lens.
Methods: A finite element model of a 30-year-old lens in the accommodated state was developed. The force necessary to achieve full accommodation in a 30-year-old lens of known external geometry was computed using this model. Two additional numerical models of the lens corresponding to the ages of 40 and 50 years were then built. Assuming that the accommodative force applied to the lens remains constant with age, the material properties of nucleus and cortex were estimated by inverse analysis.
Results: The zonular force necessary to reshape the model of a 30-year-old lens from the accommodated to the unaccommodated geometry was 0.078 newton (N). Both nucleus and cortex became stiffer with age. The stiffness of the nucleus increased with age at a higher rate than the cortex.
Conclusions: In agreement with the classical theory of Helmholtz, on which we based our model, our results indicate that a major cause of presbyopia is that both nucleus and cortex become stiffer with age; therefore, a constant value of the zonular forces with aging does not achieve full accommodation, that is, the accommodation capability decreases. |
| first_indexed | 2024-12-22T14:35:05Z |
| format | Article |
| id | doaj.art-3f6a614482ee491aa2468fb97be786b2 |
| institution | Directory Open Access Journal |
| issn | 1888-4296 |
| language | English |
| last_indexed | 2024-12-22T14:35:05Z |
| publishDate | 2012-07-01 |
| publisher | Elsevier |
| record_format | Article |
| series | Journal of Optometry |
| spelling | doaj.art-3f6a614482ee491aa2468fb97be786b22022-12-21T18:22:40ZengElsevierJournal of Optometry1888-42962012-07-015311012010.1016/j.optom.2012.05.006Hyperelastic modelling of the crystalline lens: Accommodation and presbyopiaElena Lanchares0Rafael Navarro1Begoña Calvo2Aragón Institute of Engineering Research (I3A), University of Zaragoza, Zaragoza, SpainICMA, Consejo Superior de Investigaciones Científicas (CSIC) and University of Zaragoza, Zaragoza, SpainAragón Institute of Engineering Research (I3A), University of Zaragoza, Zaragoza, SpainPurpose: The modification of the mechanical properties of the human crystalline lens with age can be a major cause of presbyopia. Since these properties cannot be measured in vivo, numerical simulation can be used to estimate them. We propose an inverse method to determine age-dependent change in the material properties of the tissues composing the human crystalline lens. Methods: A finite element model of a 30-year-old lens in the accommodated state was developed. The force necessary to achieve full accommodation in a 30-year-old lens of known external geometry was computed using this model. Two additional numerical models of the lens corresponding to the ages of 40 and 50 years were then built. Assuming that the accommodative force applied to the lens remains constant with age, the material properties of nucleus and cortex were estimated by inverse analysis. Results: The zonular force necessary to reshape the model of a 30-year-old lens from the accommodated to the unaccommodated geometry was 0.078 newton (N). Both nucleus and cortex became stiffer with age. The stiffness of the nucleus increased with age at a higher rate than the cortex. Conclusions: In agreement with the classical theory of Helmholtz, on which we based our model, our results indicate that a major cause of presbyopia is that both nucleus and cortex become stiffer with age; therefore, a constant value of the zonular forces with aging does not achieve full accommodation, that is, the accommodation capability decreases.http://www.sciencedirect.com/science/article/pii/S188842961200060XFinite element methodBiological tissuesTransversely isotropic hyperelastic behaviourLensAccommodationPresbyopia |
| spellingShingle | Elena Lanchares Rafael Navarro Begoña Calvo Hyperelastic modelling of the crystalline lens: Accommodation and presbyopia Journal of Optometry Finite element method Biological tissues Transversely isotropic hyperelastic behaviour Lens Accommodation Presbyopia |
| title | Hyperelastic modelling of the crystalline lens: Accommodation and presbyopia |
| title_full | Hyperelastic modelling of the crystalline lens: Accommodation and presbyopia |
| title_fullStr | Hyperelastic modelling of the crystalline lens: Accommodation and presbyopia |
| title_full_unstemmed | Hyperelastic modelling of the crystalline lens: Accommodation and presbyopia |
| title_short | Hyperelastic modelling of the crystalline lens: Accommodation and presbyopia |
| title_sort | hyperelastic modelling of the crystalline lens accommodation and presbyopia |
| topic | Finite element method Biological tissues Transversely isotropic hyperelastic behaviour Lens Accommodation Presbyopia |
| url | http://www.sciencedirect.com/science/article/pii/S188842961200060X |
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