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 8.5-9.5 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.