Aniridia: current pathology and management.

Aniridia is a rare panocular disorder affecting the cornea, anterior chamber, iris, lens, retina, macula and optic nerve. It occurs because of mutations in PAX6 on band p13 of chromosome 11. It is associated with a number of syndromes, including Wilm's tumour, bilateral sporadic aniridia, genitourinary abnormalities and mental retardation (WAGR) syndrome. PAX6 mutations result in alterations in corneal cytokeratin expression, cell adhesion and glycoconjugate expression. This, in addition to stem-cell deficiency, results in a fragile cornea and aniridia-associated keratopathy (AAK). It also results in abnormalities in the differentiation of the angle, resulting in glaucoma. Glaucoma may also develop as a result of progressive angle closure from synechiae. There is cataract development, and this is associated with a fragile lens capsule. The iris is deficient. The optic nerve and fovea are hypoplastic, and the retina may be prone to detachment. Aniridia is a profibrotic disorder, and as a result many interventions--including penetrating keratoplasty and filtration surgery--fail. The Boston keratoprosthesis may provide a more effective approach in the management of AAK. Guarded filtration surgery appears to be effective in glaucoma. Despite our increasing understanding of the genetics and pathology of this condition, effective treatment remains elusive.