Coloboma

Coloboma is a defect in any part of the eye. It can occur spontaneously or it can be inherited. The human eye starts to develop around the third to fourth week of pregnancy and is usually complete by the eighth week. A coloboma occurs as a result of incomplete development of any part of the baby's eyes during pregnancy. It can occur in either one eye or both eyes.

How it affects vision

The effects of a coloboma on the child's vision are dependent on where the defect is and its size. Some children have severe loss of vision whilst others see well.

Coloboma of the eyelid can range from a small gap in the eyelid (usually the top eyelid) to complete absence of the eyelid. This type of coloboma does not tend to affect vision, but the child may require extra lubricants for the eye surface to stop it from becoming too dry. In severe cases, surgery may be required to close the gap.

An iris coloboma is usually seen as a gap in the bottom part of the iris. This gap makes the pupil look like a teardrop, rounded on top and lengthened at the bottom, giving rise to the classic 'keyhole' shape. If the coloboma is limited to the iris only, children have fairly good vision but may complain of increased sensitivity to light because the pupil is larger than normal and therefore lets more light into the eye. The defect can also extend all the way to the back and affect other parts of the eye such as the lens, retina (light sensitive back surface of the eye) or optic nerve (the nerve that connects the eye to the brain).

Visual problems tend to occur when the coloboma extends more into the back of the eye affecting the retina or optic nerve.

Colobomas can be associated with a genetic condition called CHARGE which stands for:

Coloboma

Heart defects

Atresia of nasal choanae (blocking of the back of the nasal passage)

Retardation of growth and/or development

Genital and/or urinary abnormalities

Ear abnormalities or deafness

Treatment

At present, there are no medical treatments available to treat colobomas although eyelid colobomas may be surgically corrected. Children with colobomas are at an increased risk of developing raised pressures inside the eye and retinal detachment and should be monitored by an eye professional regularly. How often the child is seen will depend on where the coloboma is and how severely affected his or her vision is.