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Ralph Michael, Justin Christopher D'Antin, Laura Pinilla Cortés, Luis Pareja Aricó, Rafael I Barraquer; Cortical cataracts: The case for mechanical stress. Invest. Ophthalmol. Vis. Sci. 2017;58(8):3631.
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© ARVO (1962-2015); The Authors (2016-present)
It is known, that human cortical or cuneiform opacities are accompanied by changes in lens fiber structure and architecture mainly in the equatorial border zone between the lens nucleus and cortex. Because the lens cortex and nucleus have different viscoelastic properties in young and old lenses, we hypothesized that external forces during accommodation cause shear stress predominantly at this nucleus-cortex interface and induce cortical cataracts.
Experimentally, we studied 5 human donor lenses in a stretching device for anterior eye segments, measuring the forces and obtaining frontal images during stretching. In a literature study, we searched for a correlation between the degree of accommodation, values of refraction and the incidence of different cataract types.
Lenses with cortical cataracts showed ruptures at the nucleus-cortex interface adjacent to the cortical cataracts. Lens thickness did not changed during stretching. Lenses from pre-presbyopic donors showed no ruptures, but changed in thickness. Forces applied were of similar magnitude for all lenses tested (50 to 70 mN). Population-based studies showed that myopes (who accommodate less) have a lower risk of developing cortical than nuclear cataract. Hyperopes (who accommodate more) showed a higher risk of developing cortical than nuclear cataract. A comparative study of refraction before cataract surgery revealed that eyes with cortical cataract had a mean refraction of +2.75 and with nuclear cataract -3.75 diopters.
The ex vivo experiments indicate that the nucleus-cortex interface is vulnerable and can be separated when external forces are applied. According to literature studies, subjects more prone to accommodate developed more cortical cataract. Mechanical stress in the lens induced by accommodation may contribute to the formation of cortical cataract.
This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.
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