A choroidal nevus is a freckle inside your eye. It’s a small, pigmented spot located in the choroid, the layer of tissue that sits between the retina (the light-sensing layer) and the sclera (the white outer wall of the eye). About 4.7% of U.S. adults have one, and the vast majority never cause any problems. Most people don’t know they have one until an eye doctor spots it during a routine exam.
What a Choroidal Nevus Looks Like
Just as melanocytes in your skin can cluster to form a mole, the same type of pigment-producing cells can cluster in the choroid. The result is a flat or slightly raised gray or greenish-brown patch on the back wall of the eye, typically a few millimeters across. Your eye doctor sees it by looking through a dilated pupil with a special lens. They become more common with age: prevalence rises from about 3% in people in their 50s to roughly 7.5% in those 80 and older.
Symptoms (or Lack of Them)
Choroidal nevi almost never produce symptoms. They’re usually discovered incidentally during a dilated eye exam. In rare cases, a nevus near the center of your vision can cause fluid to leak under the retina, leading to blurred or distorted vision. Even more rarely, it can trigger abnormal blood vessel growth beneath the retina. But for the vast majority of people, a choroidal nevus is completely invisible from the inside.
Can It Turn Into Cancer?
This is the question most people really want answered, and the short answer is: almost never. The estimated annual rate of a choroidal nevus transforming into a choroidal melanoma is roughly 1 in 8,845. That’s the risk in any single year, and it makes choroidal nevi one of the lowest-risk pigmented lesions in the body. Still, because choroidal melanoma is the most common primary eye cancer in adults, eye doctors take monitoring seriously.
Ophthalmologists use a set of five warning signs, remembered by the acronym TFSOM (“To Find Small Ocular Melanoma”), to flag nevi that deserve closer attention:
- Thickness greater than 2 mm
- Subretinal fluid (fluid collecting beneath the retina near the spot)
- Symptoms such as blurred or distorted vision
- Orange pigment on the surface of the lesion
- Margin near the optic disc (within 3 mm)
A nevus with none of these features is considered low risk. Each additional feature present increases the likelihood that the spot could grow, so the combination matters more than any single sign.
How It’s Monitored
If your eye doctor finds a choroidal nevus, the standard approach is watchful waiting with periodic imaging. The two most useful tools are optical coherence tomography (OCT) and ultrasound. OCT takes a cross-sectional scan of the retina and underlying layers, making it possible to measure the nevus’s thickness precisely and to detect subtle fluid buildup that wouldn’t be visible otherwise. Ultrasound offers another way to measure thickness and track any changes over time.
A newer technique called enhanced depth imaging OCT can peer deeper into the choroid, giving a more detailed picture of the lesion’s structure. Research published in JAMA Ophthalmology found that certain features on these scans, such as disruption to the light-sensing cells overlying the spot or swelling within the retinal layers, were significantly more common in small melanomas than in benign nevi. These imaging details help your doctor distinguish a harmless freckle from something that needs intervention.
Research suggests that at least 18 months of follow-up is needed to reliably tell the difference between a stable nevus and one that’s slowly growing. For a low-risk nevus, many doctors will photograph it at the initial visit, recheck it in six months, and then move to annual monitoring if nothing has changed. Higher-risk nevi with one or more TFSOM features may be checked every three to six months.
How It Differs From Similar-Looking Spots
Not every dark spot on the back of the eye is a choroidal nevus. One common look-alike is congenital hypertrophy of the retinal pigment epithelium (CHRPE), a flat, dark patch that sits in a different layer. While a nevus forms from pigment cells within the choroid itself, CHRPE involves thickening of the very thin cell layer that lines the retina’s outer surface. Both are benign, but they behave differently on imaging and carry different (extremely low) risk profiles. Your eye doctor can usually tell them apart based on their appearance, location, and OCT characteristics.
What Happens If It Does Change
Growth is the single most important sign that a nevus may be transforming. If imaging shows that the spot has gotten thicker, developed new fluid, or gained orange pigment since the last visit, your eye doctor will likely refer you to an ocular oncologist for specialized evaluation. Treatment options for early choroidal melanoma range from targeted radiation therapy to, in advanced cases, removal of the eye, but catching changes early gives the best chance of preserving both the eye and vision. That’s why consistent follow-up matters, even though the odds of transformation are low.
For most people, a choroidal nevus is nothing more than a freckle that needs an occasional photograph. Keeping your regular eye exam schedule is the simplest way to make sure it stays that way.