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H. Michail, P. Hamilton, N. Ravi; The Development of a Uniaxial Stretcher for Measuring Mechanical Properties of the Lens . Invest. Ophthalmol. Vis. Sci. 2003;44(13):250.
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Purpose: In our continuing effort to understand the dynamics of accommodation clearly, the viscoelasticity of the lens needs to be quantitatively characterized. We have performed static stress-strain scans, and creep-recovery experiments on porcine lenses placed between two parallel plates. For more physiological methodology we custom designed a uniaxial stretcher. This will enable us to validate our static stress data and give us stress-relaxation information to further model the viscoelastic character of the lens. We also intend to use ultrasound, to follow the changes in lens thickness. Methods: Pig eyes obtained from the local abattoir were dissected, removing the cornea, and the iris. The intact lens, capsule, and small portion of sclera was left attached to the ciliary body. Tissue anchoring pins were placed in the sclera and the lens was stretched using a one-arm prototype stretcher. Runs were performed with and without the addition of cyanoacrylate glue, which was applied to the ciliary body and surrounding tissue to render them glassy and eliminate the relaxation of the zonules, ciliary body, choroids, and the sclera. The arm operates in a stress strain and stress-relaxation mode. The stress decay spectra, primarily of the lens, as a function of time was obtained for one second. Additionally, the change in the anterior to posterior polar thickness of the lens was followed by ultrasound A scan. Results: Pictured are examples of the static-stress, and relaxation curves obtained from the stretcher. The arm moves a known distance, and piezoresistive sensor measures the corresponding force exerted by the stretched lens. View OriginalDownload SlideView OriginalDownload Slide
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