Aniridia
 

Retroillumination in aniridia showing absence  of iris, the edge of the lens is clearly visible. Direct illumination of an eye with aniridia. Direct illumination of a normal  eye with dark iris for comparison

The patient has photophobia (may be wearing sun-glasses) and nystgmus (usually pendular type). The iris are  completely or rudimentary. The edges of the lens are clearly visible. There may be cataract with or without  subluxation. The cornea may contain pannus and dermoid. Tell the examiner that: you like to examine the fundus for macular hypoplasia or glaucomatous disc changes. examine the flank for nephrectomy scar for Wilm's tumour (Miller's syndrome).

Questions:

1. What is the significane of chromosome 11 in aniridia?

Answer
Deletion of the short arm of chromosome 11 in aniridia is assocaited with systemic features including Wilm's tumour, mental retardation and genitourinary abnormalities.
No all aniridia has deletion of chromosome 11. The inheritance of aniridia may be autosomal dominant, autosomal recessive or spordic.

2. What is the mechanism of glaucoma in aniridia?

Answer
In aniridia, the rudimentary iris becomes attached to the trabecular meshwork as the patients grow. This lead to impaired aqueous drainage. Glaucoma is uncommon at birth.
 

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