A choroidal nevus is similar to a birthmark or mole that occurs inside of the eye. Just like these marks can occur on your skin, they can also appear on parts of the eye. A choroidal nevus refers specifically to a mark that forms in the choroid, a layer behind the retina.

What causes a choroidal nevus?

A nevus is caused by the growth of cells called melanocytes. These cells produce the colours of your skin, hair and eyes. In your eye, the melanocytes behind your retina are normally spread out evenly. Sometimes, these cells will clump together and form a dark spot. This spot is called a nevus.

Should I be worried if I have a choroidal nevus?

Choroidal nevi are common and occur in about 5-10% of the population. Even though most nevi do not affect your vision or cause problems, they should still be watched regularly. Just like a skin mole can become cancerous, an eye nevus could do the same.

How often should the nevus be monitored?

There are certain risk factors we look for on each examination, to determine the risk of growth or malignant transformation. A choroidal nevus rarely requires treatment, but it does require monitoring, especially if risk factors are present. Photography is typically used to document the size of the nevus. A special scan (OCT) can detect fluid and an ultrasound can detect height, or whether the nevus is growing. The interval between appointments will depend on the number of risk factors a nevus displays. A nevus with no risk factors only requires annual monitoring.