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R. Michael, R. I. Barraquer, B. Willekens, J. van Marle, G. F. J. M. Vrensen; Could Cortical Cataracts Be Induced By Accommodation Forces?. Invest. Ophthalmol. Vis. Sci. 2008;49(13):3795.
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© ARVO (1962-2015); The Authors (2016-present)
Evaluation of the gross morphology, the location and the fiber cell architecture of cortical opacities in the aging human lens.
Altogether, 39 human donor lenses in the age range of 55-90 years with small focal opacities and cuneiform or spoke cataracts were obtained from the Corneabank Amsterdam. They were photographed in toto in frontal view using dark-field stereomicroscopy. Fifteen lenses were fixed, cut in axial slices and photographed the same way. Details of fiber cell architecture were investigated by fluorescent staining for membranes and by scanning electron microscopy.
Small focal and cuneiform cortical cataracts are discrete opacities located at a specific depth below the capsule, and extending from the equatorial region in anterior and posterior direction. When measured equatorially, the most superficial part of the cuneiform opacities is at a mean depth of 510 µm below the capsule. A sharp border is observed, between the opacities with their disorganized fiber architecture and the transparent more superficial cortical and deeper nuclear layers, which show a regular fiber pattern. This border is at a mean depth of 700 µm below the capsular surface. No significant relationship is found between this depth and donor age. Close examination of the opacities revealed fiber folds, fiber undulations, fiber-to-fiber separations, fiber breaks, water lakes and fiber displacement.
Small cortical and cuneiform opacities are accompanied by changes in 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 hypothesize that external forces during accommodation cause shear stress predominantly in this border zone. The location of the described changes suggests that these mechanical forces may cause fiber disorganization, small cortical opacities, and, ultimately, cuneiform cataracts.
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