A choroidal naevus cannot be seen from the outside of the eye and usually causes no symptoms. It is normally detected following a professional eye examination. A choroidal naevus (similar to a mole on the skin) occurs inside the eye in the choroid - a layer just behind the retina. Choroidal naevi occur in around 1 in 20 people in the general population. Typical naevi are small, flat and usually grey with a featureless surface. In the vast majority of cases, your practitioner will take photographs or perform an OCT examination every year. The size of the naevus will be measured and compared to previous measurements. The reason choroidal naevi are monitored is because they carry a very slight risk, as with skin moles, to evolve into Melanoma.