Common “choroidal nevus” occurs in about 5 to 10 percent of the population. A nevus, freckle, or mole can occur in the eye just like one can occur on the skin. Like the skin, the eye has melanocytes. Those are the cells that give the skin its pigment. The eye has a layer of melanocytes behind the retina in the choroid. If a number of melanocytes grow, they can form a nevus in the eye. These can only be seen by an eye care specialist who has the equipment and the skill necessary to view the back of the eye. A dilated examination is almost always necessary. Like a nevus on the skin, a choroidal nevus can grow into a malignant melanoma.
A choroidal nevus rarely requires treatment. Photography is typically used to document the size of the choroidal nevus. If the choroidal nevus has orange pigmentation, if the nevus is leaking fluid, or has a thickness of 2 mm or more, it may be (or become) a malignant choroidal melanoma.
Depending on its appearance, patients with a choroidal nevus should have their eyes examined every year. Currently, only your eye doctor can look inside your eye to see if the choroidal nevus has changed. If the choroidal nevus has orange pigment or has thickened, it should be checked more often. If a choroidal nevus is leaking subretinal fluid, this is a particularly ominous sign. Such nevi should be followed most closely for evidence of growth or malignant transformation into a choroidal melanoma. The risk of a choroidal nevus transforming into a choroidal melanoma is about 1 in 20,000.
Choroidal nevus is typically a “pigmented tumor” of the blood vessel layer (choroid) beneath the retina. A choroidal nevus is typically gray but can be brown, yellow, or variably pigmented. Your eye care professional will look to see if the choroidal nevus is raised (has thickness), has orange pigment (lipofuscin), or is leaking fluid (retinal detachment). If the choroidal nevus has one or more of these finding, it is labeled a suspicious choroidal nevus that might turn into (or be) a small choroidal melanoma.
If the choroidal nevus looks suspicious, it is reasonable to have an eye cancer specialist check it. This examination may include the use of ultrasound, specialized photography, or an intraocular angiogram. It is a good idea to keep a picture of your choroidal nevus. This picture can be compared to future examinations to help determine if the nevus has changed or stayed the same.
A choroidal nevus can have yellow-white spots on its surface called drusen. This is a sign that the choroidal nevus is preventing the eye from removing retinal waste products. It is also a sign that the choroidal nevus has been present for enough time for these products to accumulate. There are no studies that show how long it takes for drusen to form on a choroidal nevus.
A benign choroidal nevus requires no treatment and there is no way to safely remove them. Since a choroidal nevus can turn into a choroidal melanoma, it is reasonable to have it periodically observed by your eye care professional. Since skin and conjunctival melanomas have been linked to ultraviolet exposure, and since choroidal melanomas are more commonly found in patients with blue eyes, those with outdoor occupations, and those living in Australia (where there is an ozone hole), it is reasonable to wear ultraviolet (UV) blocking sunglasses. Think of sunglasses as “sun block for your eyes”.