Genetic origins of cataract

Cataract, which can be defined as any opacity of the crystalline lens, results when the refractive index of the lens varies significantly over distances approximating the wavelength of the transmitted light.1 This variation in the refractive index can result from changes in lens cell structure, changes in lens protein constituents, or both.2 Cataracts are generally associated with breakdown of the lens microarchitecture. Vacuole formation can cause large fluctuations in optical density, resulting in light scattering. Light scattering and opacity also can occur if there are significant concentrations of high-molecular-weight protein aggregates, roughly 0.1 nm or more in size. The short-range, ordered packing of the crystallins, which make up more than 90% of soluble lens proteins, is important for the maintenance of lens crystallins in a homogeneous phase. ©2007 American Medical Association. All rights reserved.