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Iris Coloboma

also known as
Ocular Coloboma
Coloboma

What is a coloboma?

Coloboma is rare eye condition in which the ocular fissure fails to close fully. This can affect all or some of the structures in the eye including the iris, lens, macular and optic nerve. Coloboma can also associated with Mircophthalmia (small eyes).

The genetics of coloboma are not fully understood, some families show dominant inheritance (Passed from parent to child), some families show recessive inheritance (present in one generation and then misses a few before reappearing) and others show no signs of inheritance.

Coloboma is sometimes associated with the following syndromes

- Iris Coloboma With Ptosis, Hyertolerlism, AND Mental Retardation
- Craniofacial Dysmorphism with Ocular Coloboma, Absent Corpus Callosum, and Aortic Dilatation
- Hirschsprung Disease, Microcephaly, and Iris Coloboma
- MCA/MR syndrome Consisting of Pre- and Post-natal Growth Retardation, Iris colobomata, Spasticity, Facial Dysmorphism, and Dilated Cerebral Ventricles.
- CHARGE syndrome.

Why is it confused with aniridia?

When the a person has iris colomboma, their pupil appears to be in the shape of a keyhole or cats eye. There is a small piece of iris missing from the lower half of the iris.

Sometimes the iris of a person with aniridia may look normal, or there may be small parts missing. This is known as atypical aniridia. The missing part may make the iris look similar to Coloboma.

A pediatric ophthalmologist should be able to make a diagnosis based on the other ocular findings. However, if the diagnosis is still unclear, genetic testing may help as aniridia is caused by a mutation in the PAX6 gene.

Support Group

If you or your child have Coloboma there is an internet based support group at

http://groups.msn.com/Coloboma