Square Arrays in Early Cortical Lens Opacities

A combined freeze-fracture and scanning electron microscopic study of early opaque spots in the aging human lens showed the absence of gap junctions and the presence of square arrays in the membranes of disturbed fibers and neighboring unaffected fibers. Square arrays, with membrane particles of 6-7 nm, are considered as rearranged gap junctions and/or intramembranous particles, with particle sizes between 8.5-9.S nm; they are a sign of electric and metabolic uncoupling. These ultrastructural observations lend support to the idea of an uncoupling mechanism in the aging human lens, conserving the transparency of unaffected parts of the lens, as postulated previously. Invest Ophthalmol Vis Sci 31:2476-2481, J990 As reemphasized by Bron and Brown, 1 most nuclear cataracts must be ascribed to increased light scattering due to increased amounts of high-molecular-weight proteins, and most cortical cataracts are the result of disturbance of the integrity of lens fibers. Cortical cataract is the most prevalent age-related type of cataract. 2 ' 3 Since cortical opacities in early stages tend to be stationary and as it is well established that lens fibers are extensively coupled by gap or communicating junctions