Cortical cataracts: the case for mechanical stress

Summary In previous publications, we found that human 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 hypothesized that external forces during accommodation cause shear stress predominantly at this nucleus‐cortex interface. The location of the described changes suggested that these mechanical forces may cause fiber disorganization, small cortical opacities, and ultimately, cuneiform cataracts. Recently, we tested our hypothesis in a stretching device for anterior eye segments from human donor eyes. Lenses with cortical cataracts showed ruptures at the nucleus‐cortex interface adjacent to the cortical cataracts. These ex vivo experiments indicate that the nucleus‐cortex interface is vulnerable and it can be separated when external forces are applied. In vivo forces from the attempt to accommodate are smaller, but a continuous action during years may induce micro ruptures at this interface which may lead to cortical cataract.