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This Article Full Text Full Text (PDF) All Versions of this Article: iovs.07-1647v1 49/10/4490    most recent Submit a response Alert me when this article is cited Alert me when eLetters are posted Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Google Scholar Articles by Ziebarth, N. M. Articles by Parel, J.-M. PubMed PubMed Citation Articles by Ziebarth, N. M. Articles by Parel, J.-M.

Role of the Lens Capsule on the Mechanical Accommodative Response in a Lens Stretcher

¹From the Ophthalmic Biophysics Center, Bascom Palmer Eye Institute, University of Miami Miller School of Medicine, Miami, Florida; the ²Biomedical Optics and Laser Laboratory, Department of Biomedical Engineering, University of Miami College of Engineering, Coral Gables, Florida; ³Advanced Medical Optics, Santa Ana, California; the ⁴Vision Cooperative Research Centre, Sydney, NSW, Australia; and the ⁵Department of Ophthalmology, University of Liège, CHU (University Hospital Centre) Sart-Tillman, Liège, Belgium.

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 ± 17years; 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 · 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.