Aniridia
Aniridia refers to partial or complete absence of iris tissue in the eye. It is usually associated with poor vision due to fovea and optic nerve hypoplasia. Aniridia can be familial or sporadic.
What is aniridia?
Aniridia refers to partial or complete absence of iris tissue in the eye. It is usually associated with poor vision due to fovea and optic nerve hypoplasia. Aniridia can be familial or sporadic.
What cause aniridia?
The PAX6 gene is responsible for the normal development of the anterior part of the human eye. A mutation of the PAX6 gene causes malformation of tissue structure in the front part of the eye (including iris tissue) and results in aniridia.
What are the symptoms and signs of aniridia?
Children with aniridia often present with poor vision, nystagmus and light sensitivity due to absence of iris tissue.
What are the ocular associations with aniridia?
Congenital glaucoma occurs in over 50% children with aniridia. Dry eyes are common among aniridia patients due to cornea limbal stem cell deficiency, cataract or lens subluxation.
What are the systemic associations of aniridia?
Wilms’ tumour (a tumour of the kidney) can occur due to a larger deletion of the chromosome 11 involved both the Wilms tumour gene and PAX6 gene because of their proximity. Children with sporadic aniridia are at higher risk of developing Wilms tumour and those with familial aniridia are usually not.
What are the treatments of aniridia?
Children with aniridia have life long risk of developing glaucoma and other ocular complications, such as dry eyes and cataract. They need regular examination and treatment by ophthalmologists. Genetic testing for the Wilms tumour gene is an important part of the management of children with aniridia. Unless chromosome deletion is excluded, children with sporadic aniridia need regular review by paediatricians for surveillance of possible development of Wilms tumour.
Educational Implications
Behaviours or conditions that might indicate aniridia
- Nystagmus
- Photophobia
- Large pupil that may be misshapen.
- Blurred vision.
- Glare
- Cataracts
- Cloudy cornea due to raised intraocular pressure.
- It is important to remember that a young child with aniridia, particularly if the child’s vision condition has been stable from birth, may not be aware that what he/she is seeing is any different from what other children see. A gradual visual loss is also difficult for a child with aniridia to detect and verbalise. For example, the child may not realise that there is increased glaucoma pressure in their eyes.
What to do
- The young person should visit an ophthalmologist to determine diagnosis and treatment.
- May need to use sunglasses or hats outdoors and indoors.
- Allow time for adjustment to lighting changes.
- Provide seating in the front of the classroom with back to windows.
- Reduce glare.
- A lamp for direct lighting may be required.
- Use magnification.
- Paper with bold lines may help.
- Bold black markers are recommended for the whiteboard.
- Use a slope board.