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Aniridia

What is Aniridia?
Aniridia is a rare congenital eye condition causing incomplete formation of the iris. This can cause loss of vision, usually affecting both eyes.

In Aniridia, although not entirely absent, all that remains of the iris, the coloured part of the eye, is a thick collar of tissue around its outer edge. The muscles that open and close the pupil are entirely missing. The appearance of a "black iris" is the result of the really enormous pupil.


Causes
There is no single cause for this eye condition that falls roughly into two groups, one of which is hereditary and the other of unknown origin.

Aniridia can result from autosomal dominant or autosomal recessive inheritance or may occur on its own.

Autosomal dominant individuals in this group will be unlikely to have additional health or developmental problems and may have normal or poor vision. Autosomal dominant problems result from one of a pair of matched genes being normal whilst the other carries the abnormality. There is a 1 in 2 chance of inheritance in each such pregnancy. Usually several individuals in successive generations will be affected.

Autosomal recessive inheritance carries a risk of accompanying learning disabilities. Autosomal recessive problems arise when both parents carry the abnormal gene although they are unaffected. There will be a 1 in 4 inheritance risk in each pregnancy. Usually this only affects siblings within a single generation.


Effects
The effects will vary considerable between individuals and differing causes.

Rarely Aniridia may be associated with a tumour of the kidney called Wilm's. This type is sporadic although it has been associated with chromosomal disorder and may increase risk of other developmental flaws. The Wilm’s tumour can normally be treated very successfully.

Some babies with Aniridia might be sensitive to light, whilst others might experience clouding of the lens so it is important to seek advice about protecting your baby's eyes should the eye specialist feel that these conditions may arise.

Aniridia may be associated with other eye conditions such as nystagmus, glaucoma, corneal disease, cataract, lens sublaxation (dislocation), macula and optic nerve disease.


Further information

 

 



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