Role of the lens capsule on the mechanical accommodative response in a lens stretcher
| Autor: | Mohamed Aly, Jean-Marie A. Parel, Isabelle Dortonne, Noel M. Ziebarth, Derek Nankivil, Esdras Arrieta, David Borja, Fabrice Manns, Rakhi Jain |
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| Rok vydání: | 2008 |
| Předmět: |
Adult
Male Accommodative response Aging Materials science Adolescent medicine.medical_treatment Lens Capsule Crystalline Article law.invention Ciliary body law Lens Crystalline medicine Animals Humans Child Capsulorhexis Aged Lens capsule Capsule Accommodation Ocular Presbyopia Anatomy Middle Aged medicine.disease Elastic Tissue Elasticity Sclera Lens (optics) Macaca fascicularis medicine.anatomical_structure Elasticity Imaging Techniques Female Stress Mechanical Biomedical engineering |
| Zdroj: | Investigative ophthalmologyvisual science. 49(10) |
| ISSN: | 1552-5783 |
| Popis: | Purpose To determine whether changes in elastic properties of the lens capsule ex vivo with age contribute to the forces necessary for accommodation. Methods Postmortem human (n = 22; age average: 41 +/- 17 years; range: 6-7) and cynomolgus monkey (n = 19; age average: 7.7 +/- 1.8 years, range: 4.2-10) tissues including the lens, capsule, zonules, ciliary body, and sclera were mounted in an optomechanical lens-stretching system. Starting at 0 load, the sclera was symmetrically stretched to 2 mm in 0.25-mm steps at a speed of 0.1 mm x s(-1). The load and lens diameter were measured at each step. The lens contents were removed through a mini-capsulorhexis. The stretching cycles were repeated on the empty capsular bag. The forces necessary to stretch the natural lens and empty bag were quantified as a function of age and compared. Results The force needed to stretch the empty lens capsule was independent of age (human, 2.6-34.9 g/mm [25.2-342.7 mN/mm]; monkey, 8.2-21.3 g/mm [80.3-208.6 mN/mm]). The ratio of the force necessary to stretch the empty lens capsule to the force necessary to stretch the natural lens decreased with age in the human and monkey lenses (P = 0.003, P = 0.72, respectively). Conclusions The mechanical properties of the empty lens capsule assessed ex vivo in a lens stretcher remain constant with age, suggesting that the changes in elasticity of the lens capsule do not play a significant role in presbyopia. In young eyes, the lens capsule determines the force necessary to stretch the whole lens. The age-related increase in force needed to stretch the lens is due to changes in the lens contents. |
| Databáze: | OpenAIRE |
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