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N. M. Ziebarth, E. Arrieta, F. Manns, V. T. Moy, R. C. Augusteyn, J.-M. Parel; Primate Lens Capsule and Cortex Elasticity Assessed by Atomic Force Microscopy. Invest. Ophthalmol. Vis. Sci. 2009;50(13):4379.
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© ARVO (1962-2015); The Authors (2016-present)
To measure the elasticity of the capsule and cortex of human and non-human primate cadaver lenses using atomic force microscopy (AFM).
AFM elasticity measurements of the anterior lens capsule and outer lens cortex were performed on 13 cynomolgus monkey (2.4-9.2 years), 5 hamadryas baboon (3-21 years), and 14 human lenses (34-90 years). The inner lens cortex of 1 cyno and 1 human was also measured. Anterior capsule specimens were obtained by performing a 5mm continuous curvilinear capsulorhexis. The capsular disk was soaked in 0.1% trypsin and 0.02% EDTA for five minutes to remove the epithelial cells, placed on a Petri dish and immersed in DMEM. After removal of the anterior capsule, the lens with exposed cortex was placed in a Petri dish and immersed in DMEM. The inner cortex was exposed by performing a 1.2mm deep cut with a clinical femtosecond laser (Intralase, AMO) and removing the cut anterior lens tissue. Elasticity was measured with a custom-built laboratory AFM designed for mechanical testing of ophthalmic tissues. The capsular specimens and the exposed cortical surfaces were probed with an AFM cantilever tip. Young’s modulus was calculated using the model of Sneddon for a conical indenter.
Young’s modulus of the anterior lens capsule ranged from 7.88 to 62.4kPa for non-human primates and from 21.5 to 126kPa for humans. The elastic modulus of the capsule of human and non-human primates increases with age (p=0.078 and 0.016, respectively). Young’s modulus of the outer lens cortex ranged from 0.066 to 3.40kPa for non-human primates and from 0.075 to 1.27kPa for humans, and was not a function of age. Young’s modulus of the inner lens cortex was 3.65kPa (human) and 42kPa (cyno).
The lens capsule becomes stiffer with age, but the outer lens cortex elasticity remains constant with age. The lens capsule is 1 to 2 orders of magnitude stiffer than the anterior cortex. The lens capsule and cortex elasticity of humans and non-human primates is comparable.Support: NSF Graduate Student Fellowship (NZ); NIH EY14225; Florida Lions Eye Bank; the Australian Government CRC Programme through the Vision CRC, Sydney Australia; Rakhi Jain, PhD, AMO Inc, Santa Ana, CA; NIH center grant P30-EY014801; Research to Prevent Blindness. NSF-BITC (VM); NIH GM55611(VM); Scientific Advisory Committee, University of Miami; Henri and Flore Lesieur Foundation (JMP).
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