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Valas Teuma, Gary Gray, Keith Edwards, Steve Bott, Randy Frey; Improving Presbyopic Eye Accommodative Response by Softening Mid-Periphery of the Crystalline Lens via Ultra-Fast Laser. Invest. Ophthalmol. Vis. Sci. 2011;52(14):850.
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The purpose of the study is to explore the utility of using a femtosecond laser to restore accommodative capacity through softening of the mid-periphery of crystalline lens tissue, in custom shapes designed to increase lens curvature in the accommodated state. The curvature would then decrease under zonular tension for distance vision.
Finite Element Analysis was used to generate models of human lenses representing subjects of ages 35, 45 and 55 years old. The models were used to predict refractive change and accommodative response when a volume of lens tissue of a specific shape in the lens mid-periphery was softened. A femtosecond laser was programmed to deliver custom shot patterns designed to photodisrupt lens tissue in a manner resembling that of the shapes predicted by the FEA modeling to generate the highest accommodative response. Laboratory testing was conducted on porcine eyes to compare the changes in anterior lens curvature resulting from application of the custom shot patterns with the FEA prediction. The same custom shot patterns were applied in clinical trials to human subjects with refractive changes measured subjectively and objectively.
FEA predicts refractive power increases of 3.5 D and 3.6 D, respectively, for the 45 YO and 55 YO presbyopic model eyes. The change for a 35 YO normal eye was much smaller: 2 D. The femtosecond laser-treated porcine eyes showed an average 1.5D increase of refractive power. Clinical treatment of the eyes of human subjects with the same custom patterns resulted in significant increases in refractive power measured both subjectively and objectively.
Finite Element Modeling predicts that femtosecond lasers can be used to change lens curvatures by altering biomechanics of tissue in the mid-periphery of the lens and further predicts accommodative response when the treated model lens is not subjected to zonular tension. Femtosecond lasers applying custom patterns to porcine lenses and to eyes of human subjects resulted in increases in refractive power in reasonable agreement with the FEA predictions.
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