A choroidal nevus is a common, benign pigmented spot inside the eye, similar to a mole on the skin. These spots are harmless and do not affect vision. They are often discovered incidentally during a routine eye examination. Monitoring them helps ensure long-term eye health.
Understanding Choroidal Nevi
A choroidal nevus is a non-cancerous pigmented lesion located in the choroid. The choroid is a layer of blood vessels and connective tissue situated between the retina, which senses light, and the sclera, the eye’s white outer layer. This placement means the nevus is deep within the eye, not visible to the naked eye.
These nevi appear as flat, dark, round or oval areas. Their color can vary, appearing slate-gray, brown, or yellowish. Choroidal nevi are common, affecting about 5% to 10% of adults. While they can be present from birth, they are more commonly detected in adulthood.
How Choroidal Nevi are Found
Choroidal nevi are discovered during a routine dilated eye examination by an ophthalmologist or optometrist. Specialized instruments, such as an ophthalmoscope, are used to view the back of the eye and identify pigmented spots. Since these nevi rarely cause symptoms, most individuals are unaware of their presence until an eye doctor spots them.
For a more detailed evaluation, advanced imaging techniques may be used. These include optical coherence tomography (OCT), which provides high-resolution cross-sectional images of the retina and choroid, or fundus photography, which captures detailed pictures of the back of the eye. Ultrasound may also be used to measure the nevus’s thickness and assess its internal structure. These tests are non-invasive and painless, providing information about the nevus’s characteristics.
Distinguishing Nevus from Melanoma
While a choroidal nevus is benign, there is a small risk it could transform into a choroidal melanoma, a type of eye cancer. The annual rate of transformation is estimated to be approximately 1 in 8,845 nevi. Ophthalmologists look for specific characteristics to differentiate a benign nevus from a suspicious lesion or an early melanoma.
Features that raise concern for potential malignant transformation include:
A thickness greater than 2 millimeters or a basal diameter larger than 5 millimeters.
Fluid accumulation under the retina or orange pigment on the nevus’s surface.
Symptoms like decreased vision, flashes of light, or floaters.
A location close to the optic disc.
An ultrasonographic appearance of hollowness within the lesion.
Ongoing Care and Monitoring
Once a choroidal nevus is identified, regular follow-up appointments monitor for any changes that might indicate transformation. The frequency of these appointments can vary, often starting every 6 to 12 months, and then annually if the nevus remains stable. These visits involve dilated eye exams and include repeat imaging tests, such as fundus photography or OCT, to track the nevus’s size and other features over time.
Individuals should contact their ophthalmologist if they notice any new visual symptoms. These include flashes, floaters, blurred vision, or a blind spot, as such changes might signal a transformation of the nevus. Benign nevi do not require treatment, but if a nevus shows signs of transforming into a melanoma, treatment options for melanoma, such as radiation therapy or laser therapy, would be discussed by an ocular oncologist.