What is it?
Ocular coloboma (or just ‘coloboma’) means that there is a gap at the base of the eye. It’s rare – about 1 in 10,000 births are affected – but it accounts for up to 10 percent of childhood blindness.
Coloboma happens during pregnancy (at around 6-8 weeks). The lower-most parts of the light-sensitive layer of the eye (the retina) fail to develop properly. Instead of fusing together, there is a gap which can extend from the coloured part of the eye at the front (the iris) through to the specialised cable that sends visual signals from eye to brain (the optic nerve) at the back.
It can affect one or both eyes and may be more severe in one eye than the other. It is usually diagnosed in newborn babies.
Doctors and scientists think that coloboma is mainly genetic, but in many cases the genetic fault has not been discovered. This means we still know very little about the precise causes of coloboma, but it’s likely that environment (e.g. lifestyle and infections during pregnancy) may also play a part.
Coloboma can happen when there is no family history of it, or it can be inherited. It may also be part of syndromes that affect other parts of the body and linked to additional eye conditions.
Parents of children with coloboma are often examined to see if they also have a mild version of it, to find out if it was inherited.
If the gap extends back into the eye it can severely affect vision, especially if it affects the retina and optic nerve. But many people with coloboma may not know that they have it, as there may not be any symptoms.
The most common form of coloboma does not affect vision – the only sign of it is a keyhole-shaped gap in the iris.
There are no treatments yet for sight loss due to ocular coloboma of the retina or optic nerve. But support can be given to help people make the best use of the vision they have. The affected eye may need to be protected from damage by direct sunlight.
A full ophthalmological examination is usually done if coloboma is suspected at birth.
Ocular coloboma research aims to find out more about the genes needed for eye development and to develop treatments that could prevent coloboma. Finding the relevant genes is also important for good diagnosis and genetic counselling.Read our research projects
Last updated September 2015
Dr Joe Rainger, University of Edinburgh