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L.S. Kwok, B.K. Pierscionek; Lens Stress Forces . Invest. Ophthalmol. Vis. Sci. 2005;46(13):2913.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: To investigate the spatial variation of biomechanical forces in the human lens. Methods: The superficial anterior human lens was modeled using thin membrane theory. An ellipsoid of revolution was used to represent the human lens, of 8 mm diameter and 1.6 mm sagittal half–thickness. Radial (meridional, N<font face="symbol">f</font>) and hoop forces (Nθ) were calculated and normalized to internal lens pressure. Results: Radial forces were tensile from the anterior lens pole to the equator (N<font face="symbol">f</font>>0), dropping nonlinearly from a maximum at the pole to one–third maximum at the equator. Hoop forces were initially tensile (Nθ>0) in the central anterior lens, dropping to zero at 22.7° azimuth angle (central 6.8 mm dia), and became compressive towards the equator (Nθ<0). The absolute ratio of pole:equator hoop forces exceeded 2. Conclusions: These results indicate that cells in the central 6.8 mm dia anterior zone of the lens are subjected to tensile radial and tensile hoop forces. This dual tensile loading would favour centrifugal migration of lens epithelial cells. During accommodation these tensile forces could exert significant moulding forces on the epithelium and superficial cortex. Nearer to the lens equator, lens cells experience tensile radial forces, but with compressive hoop forces. These combined forces would favour radial alignment and may contribute to the curious ordering of lens fibres in radial columns. The radial and hoop forces in a thin shell are influenced by lens thickness and equatorial diameter. Thus, the spatial variation of N<font face="symbol">f</font> and Nθ may be affected by aging.
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