About 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 of Aniridia
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.
Risk factors or groups for Aniridia
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 one in two 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 one in four inheritance risk in each pregnancy. Usually this only affects siblings within a single generation.
Effects of Aniridia
The effects will vary considerable between individuals and differing causes.
Rarely Aniridia may be associated with a tumour of the kidney called Wilms'. 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.
Treatments
Babies with Aniridia will need to be carefully and regularly examined to ensure no supplementary problems develop.
Where treatment is offered this will relate to problems additional to the absent iris. In some individuals, loss of vision may increase risk of other problems and it is advisable, during the first five years of life, that careful attention be paid to identify whether other complications develop which may require treatment.
Genetic implications
As with all health conditions present at birth it is wise to seek advice from a genetic counsellor in order to identify implications for family members. Your GP or hospital eye specialist will be able to advise on local genetic services.
What next
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