Aniridia

Aniridia is a rare congenital condition characterised by the partial or complete absence of the iris. This results in a very large pupil and often severely impaired vision.

Genetics and Inheritance

Aniridia is most often caused by mutations in the PAX6 gene on chromosome 11p13, which is crucial for eye development. It is usually inherited in an autosomal dominant manner, but rare autosomal recessive forms exist (e.g., Gillespie syndrome). Homozygous mutations are typically fatal.

Associated Syndromes

WAGR syndrome: Wilms tumour, Aniridia, Genitourinary anomalies, and intellectual disability.
Gillespie syndrome: Aniridia, cerebellar ataxia, and mental deficiency.

Symptoms and Complications

Poor vision (not always present)
Extreme light sensitivity (photophobia)
Nystagmus (involuntary eye movement)
Strabismus (misalignment of the eyes)
Increased risk of cataracts, glaucoma, foveal and optic nerve hypoplasia

Treatment

Treatment is supportive and may include tinted lenses, low vision aids, and, in some cases, artificial iris implants (e.g., CustomFlex Artificial Iris). Early intervention for associated complications is crucial.

Evolutionary Note

The PAX6 gene is highly conserved across animal species and is a master regulator of eye development.

Writing Tips (Expanded)

Aniridia can be used to explore themes of vulnerability, difference, or disability.
Sensory detail: describe the impact of light, the appearance of the eyes, and emotional responses to visual challenges.
Consider referencing associated syndromes for realism.

Features

May cause extreme sensitivity to light (photophobia), reduced visual acuity, and increased risk of other eye problems.
The iris may appear almost absent on superficial examination.

Writing Tips

Aniridia can be used to explore themes of vulnerability, difference, or disability.
Sensory detail: describe the impact of light, the appearance of the eyes, and emotional responses to visual challenges.