Genetic Origins of Cataract

ataract, which can be defined as any opacity of the crystalline lens, results when the refractiveindexofthelensvariessignificantlyoverdistancesapproximatingthewave- length 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 Cata- racts 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 ag- gregates,roughly0.1nmormoreinsize.Theshort-range,orderedpackingofthecrystallins,which make up more than 90% of soluble lens proteins, is important for the maintenance of lens crys- tallins in a homogeneous phase.