What is iris coloboma?

Q.   My daughter has an iris coloboma.  What are the causes of this and what are the visual consequences?

A.   An iris coloboma produces a different shaped pupil which can be described as an upside down pear shape or a cat’s eye pupil.

It is due to an incomplete closure of the optic fissure during the 5th week of gestation.  Isolated findings within families indicate a sporadic inheritance (non-genetic) while some families show an autosomal dominant inheritance pattern.  It occurs in 1 out of 10,000 births.

Depending on the extent of the incomplete optic fissure closure, the coloboma may only affect the pupil but it can also extend to the optic nerve and retina.

Vision is generally good as long as the macula (central vision portion of the retina) is not affected by the coloboma.  Some light sensitivity may be associated with an iris coloboma as light may scatter more in the peaked portion of the pupil.  UV protected sunglasses are strongly recommended.


Dr. Patricia Fink


Millcroft Shopping Centre
2080 Appleby Line, Unit E6
Burlington, Ontario, L7L6M6
Tel: (905) 319-1066