Aniridia

Aniridia is a rare eye condition marked by the complete or near-complete absence of the iris, the colored ring of muscle that normally controls how much light enters the eye by adjusting the size of the pupil. The disorder is usually caused by mutations affecting the PAX6 gene on chromosome 11, a gene essential to eye development, and it follows an autosomal dominant inheritance pattern in most families, meaning a child of an affected parent has roughly a fifty percent chance of inheriting it, though some cases arise from new mutations or rare recessive forms. Aniridia rarely involves only the iris: the macula, optic nerve, cornea, and lens are often underdeveloped as well, which is why vision problems in affected people usually go well beyond light sensitivity and can include poor central vision and involuntary eye movements. In a minority of cases aniridia appears as part of a broader syndrome, most notably WAGR syndrome, which also involves a higher risk of kidney cancer and developmental delay, or Gillespie syndrome, which adds problems with balance and coordination. Lifelong monitoring is recommended because of the elevated risk of glaucoma and other complications.