any opacity in the lens of the eye that results in blurred vision. Cataracts may be congenital or acquired. The latter may be due to metabolic disease (such as diabetes), direct or indirect injury to the lens, or prolonged exposure of the eye to infrared rays (e.g. glass-blowers' cataract) or ionizing radiation, but they are most commonly a result of age (senile cataract). A type commonly related to ageing is nuclear sclerotic cataract, which results from increasing density and yellowing of the centre of the lens. A posterior subcapsular cataract, which develops at the rear surface of the lens within the lens capsule, is also related to ageing but occurs in addition with prolonged use of steroids and chronic ocular inflammation. Brunescent cataracts are dark brown and very dense, and a cortical cataract is one in which the opacity occurs in the soft outer part (cortex) of the lens. A Morgagnian cataract is a longstanding very opaque cataract in which the cortex has started to shrink and liquefy, leaving a central shrunken nucleus. Minor degrees of cataract do not necessarily impair vision seriously.
Cataract is treated by removal of the affected lens (see cataract extraction, phacoemulsification); patients may wear a contact lens or appropriate spectacles to compensate for the missing lens but in modern practice a synthetic intraocular lens implant is routinely placed inside the eye after surgery.

The new mediacal dictionary. 2014.

, , / , (from opacity of the crystalline lens)