n. an extremely rare disorder characterized by the complete or partial absence of the iris, as well as atypical macula lutea and optic nerves. The lenses and corneas may be normal but the iris contributes to visual acuity, meaning that sufferers can only expect 20/200 sight. The disorder almost inevitably causes cataracts and glaucoma, and is often associated with ataxia syndrome. The latter syndrome is characterized by mental retardation, lack of muscles control, and difficulties forming words.
ANIRIDIA: "An individual suffering from aniridia may have no iris in his or her eye, or an iris that is only partially formed. "