Cataracts, lens substitutes, and federal regulation.

The crystalline lens of a normal eye sometimes becomes opaque, often as a consequence of aging. This condition is termed a cataract. Once a cataract has been removed, a lens substitute must be used to restore vision. The substitute may be a lens placed in front of the eye (spectacles), on the surface of the eye (contact lens), or inside the eye (intraocular lens). For many patients, intraocular lenses may be more effective than the other lenses, but may also involve greater risks.