A coloboma is a gap in one of the eye's structures, such as the iris, retina, optic disc or choroid. Colobomas affect approximately one in every 10,000 people and the impact on vision can range from very small to causing blindness. Colobomas are congenital, meaning they are present from birth, and are caused when a baby's eyes do not develop properly during pregnancy. More specifically, a gap in the eye called the choroid fissure fails to close before the baby is born. A coloboma can be present in one or both eyes, as well as the eyelids, and is often located at the bottom of the eye, creating a characteristic keyhole-shaped pupil.

Coloboma severity

The effect a coloboma has on vision will depend on the location of the gap and how big it is. In the least severe cases, the gap will have closed throughout the back and centre of the eye and will only affect the front. Colobomas affecting the iris are the most common and usually have a limited impact on vision. However, individuals with this type of gap may experience a dislike of bright lights. This is because the iris restricts the amount of light entering the pupil and this function can be disrupted by a coloboma. When too much light enters the eye, it causes discomfort and could distort images. If this is the case, tinted glasses, sun blinds and other measures may be used to ease the problem. The further the coloboma goes back into the eye, the more likely vision will be adversely affected - particularly when the retina is involved. This could result in severe issues with reading, writing and other activities that demand great attention to detail.

Coloboma treatment

There is no treatment for coloboma at present, although children born with colobomas will receive specialist care at a hospital in their early years to monitor the condition and track the effects on their overall eye health. Colobomas can be linked to other birth defects, including CHARGE syndrome. This rare condition affects the heart, nose, ears, genitals and overall growth of a child. Hospital and medical staff will be able to diagnose these issues early if they are present. People with colobomas are more prone to retinal detachments and glaucoma, which can be treated if they occur. Glasses may also be required to correct short- or long-sightedness, although they will not help with vision problems directly caused by the coloboma. Certain cosmetic options also exist, such as contact lenses that cover the keyhole shape and give the pupil a rounded appearance.