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N.M. Ziebarth, E. Wojcikiewicz, F. Manns, V. Moy, J.–M. Parel; In situ Measurement of Capsule Elasticity of Cadaver Lenses Using Atomic Force Microscopy . Invest. Ophthalmol. Vis. Sci. 2006;47(13):5852.
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© ARVO (1962-2015); The Authors (2016-present)
To demonstrate the feasibility of in situ lens capsule elasticity measurements on intact lenses using atomic force microscopy (AFM).
AFM elasticity measurements were performed on intact capsules of 5 non–fixed cadaver cynomolgus eyes (4–10 years, <1 day postmortem) and 1 non–fixed cadaver rhesus eye (16 years, 3 hours postmortem) that were left attached to the zonule–ciliary body–sclera framework. The eyes were prepared by bonding a plastic ring on the sclera after removal of conjunctiva, adipose, and muscle tissues. The posterior pole was sectioned, excess vitreous was removed, the eye’s anterior section was placed on a Teflon slide to protect the posterior pole of the lens, and the cornea and iris were sectioned. The lens–zonule–ciliary body–sclera section was then placed in a Petri dish filled with BSS in a laboratory–built AFM system designed for force measurements (Wojcikiewicz et al, J Cell Science, 2003). The AFM is shielded inside an acoustic/vibration isolation chamber. The central pole of the lens capsule anterior surface was probed with the AFM cantilever tip. The deflection of the cantilever is proportional to the force that the AFM probe tip exerts on the sample. The recorded cantilever deflection–indentation curves were used to derive force–indentation curves for the capsule after factoring out the deflection of the cantilever on a hard surface. Young’s modulus was calculated from the force–indentation relation using the model of Hertz (Hertz, J Reine Angewandte Mathematik 1881).
The average value of Young’s modulus was 471N/mm2 (range: 62–1591N/mm2). Previous researchers using uniaxial stretching found a Young’s modulus between 0.3–10 N/mm2 (Fisher, J Physiology, 1969; van Alphen and Graebel, Vision Research, 1991; Krag and Andreassen, IOVS, 1997; Danielsen et al, Exp Eye Research, 2004). These differences require further investigation but are probably due to anisotropic properties of the lens capsule and differences in the methodology.
AFM can be used to provide sensitive measurements of the lens capsule elasticity in situ. Support: NSF Graduate Student Fellowship; NIH EY14225; Florida Lions Eye Bank; Vision CRC, Sydney Australia; NIH center grant P30–EY014801; Research to Prevent Blindness.; Henri and Flore Lesieur Foundation; NSF–BITC; NIH GM55611.
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