Choroidal Nevus: Understanding a Freckle in Your Eye
Understanding Choroidal Nevus
A choroidal nevus is a flat or slightly raised collection of pigmented cells located in the choroid. The choroid is a thin layer of blood vessels and tissue that sits between the retina and the sclera (the white outer wall of the eye). These spots are usually dark brown or gray, well-defined, and discovered during a routine dilated eye exam.
Most nevi are small, measuring less than 5 millimeters across. They remain stable throughout a person's life. They do not affect vision unless they are located directly beneath the macula, the central part of the retina responsible for sharp, detailed sight.
Choroidal nevi arise from melanocytes, the cells in the choroid that produce pigment. Certain genetic mutations, particularly in genes called GNAQ and GNA11, have been found in these pigmented cells. These same mutations are also present in a majority of uveal melanomas. This is one reason a retina specialist monitors nevi carefully over time.
In most cases, the nevus remains stable. Rarely, additional genetic changes may cause a nevus to grow. When this happens, the nevus can damage the overlying retinal pigment epithelium (RPE), a layer of cells that supports the retina. This damage may allow fluid to accumulate under the retina. It may also lead to abnormal blood vessel growth known as choroidal neovascularization.
Although the vast majority of choroidal nevi are benign (non-cancerous), a very small number can transform into choroidal melanoma, a type of eye cancer. The rate of transformation is estimated at approximately 1 in 9,000 per year (ASRS, 2024). Because the change from a benign nevus to melanoma can be slow and subtle, periodic imaging and eye exams allow a retina specialist to detect any changes early.
Who Is Affected and Risk Factors
Choroidal nevi are relatively common in adults. In the United States, approximately 5% of adults aged 40 and older have a choroidal nevus (ASRS, 2024). Prevalence varies by race and ethnicity. Studies report that approximately 5.6% of White individuals, 2.7% of Hispanic individuals, and 0.6% of Black individuals have a choroidal nevus (ASRS, 2024). In Asian populations, the estimated prevalence ranges from 1.8% to 2.9% (ASRS, 2024).
Several health and lifestyle factors have been linked to the presence of choroidal nevi. Research has identified the following associations:
- Higher body mass index (BMI)
- Higher lifetime exposure to unopposed estrogen
- Hypertension (high blood pressure)
- Psoriasis
- Lower levels of high-density lipoprotein (HDL, or 'good' cholesterol)
- Higher uric acid levels
While most choroidal nevi remain stable, certain features increase the risk that a nevus could transform into melanoma. Retina specialists use a well-known mnemonic called TFSOM-DIM. It stands for 'To Find Small Ocular Melanoma Doing Imaging' and highlights the key warning features (Shields et al., 2023):
- Thickness greater than 2 mm on ultrasound
- Subretinal Fluid visible on optical coherence tomography (OCT)
- Symptoms such as vision loss to 20/50 or worse
- Orange pigment (lipofuscin) seen on imaging
- Melanoma hollow pattern on ultrasound
- Diameter greater than 5 mm on photography
A large study of 2,355 cases found that the five-year risk of transformation depends on how many of these features are present. With no risk factors, the five-year risk is approximately 1% (Shields et al., 2023). With one factor, the risk rises to a notable percentage (Shields et al., 2023). With two factors it reaches a substantial proportion (Shields et al., 2023). With three or more factors the risk exceeds a substantial proportion (Shields et al., 2023). Giant nevi, those measuring 10 mm or more across, carry an even greater risk of change.
Signs and Symptoms
Most choroidal nevi produce no symptoms at all. A person typically does not know they have one until a retina specialist or eye care provider discovers it during a dilated eye exam. This is one of the reasons regular eye exams are valuable, even when vision seems normal.
In some cases, a nevus located beneath the macula can lead to blurred or distorted central vision. This may happen if the nevus causes changes in the overlying RPE, leading to fluid buildup under the retina. Some people may notice a gray or dark spot in their vision. Choroidal neovascularization, the growth of abnormal blood vessels associated with the nevus, can also cause fluid leakage or bleeding that affects sight.
Certain symptoms may indicate that a nevus is changing or that a separate eye condition needs immediate evaluation. See a retina specialist or go to the emergency room immediately if you experience any of the following:
- A sudden increase in floaters (spots or threads drifting in your vision)
- Flashes of light in one eye
- A shadow or curtain spreading across part of your vision
- Sudden loss of vision in one eye
Diagnosis and Testing
A choroidal nevus is most often discovered during a comprehensive dilated eye exam. After dilating the pupil with eye drops, the retina specialist examines the inside of the eye using a special lens and light. The nevus appears as a flat or slightly elevated pigmented spot on the choroid.
Once a nevus is identified, a retina specialist may use several imaging tools to document its size, shape, and features. These tests help establish a baseline for future comparison and assess any features that may indicate risk of transformation.
- Fundus photography: A high-resolution photograph of the back of the eye used to measure the diameter of the nevus and track changes over time.
- Optical coherence tomography (OCT): A non-invasive scan that creates detailed cross-sectional images of the retina. OCT can detect subretinal fluid or changes in the RPE overlying the nevus.
- Fundus autofluorescence (FAF): A specialized imaging technique that can reveal orange pigment (lipofuscin) on or around the nevus. This feature is linked to higher transformation risk.
- Ultrasonography (ultrasound of the eye): A painless test that measures the thickness of the nevus. It can identify internal characteristics such as a melanoma hollow pattern.
Recent developments include a new online ocular oncology reading center designed to help evaluate nevus risk. Using the TFSOM-DIM criteria and multimodal imaging results, these tools help retina specialists assess the likelihood of transformation and determine appropriate monitoring intervals.
Treatment Options
The majority of choroidal nevi do not require any active treatment. The standard approach is careful observation with periodic imaging and eye exams. A retina specialist will typically schedule follow-up visits every 6 to 12 months, depending on the size and features of the nevus. At each visit, imaging tests are compared to the baseline to look for any signs of growth or new risk features.
When a choroidal nevus causes complications such as choroidal neovascularization or subretinal fluid, treatment may be needed to protect vision. The two main approaches are anti-VEGF therapy and photodynamic therapy (PDT).
Anti-VEGF therapy involves intravitreal injections (injections directly into the eye) of medications that block vascular endothelial growth factor. This protein drives abnormal blood vessel growth and fluid leakage. Medications used for this purpose include Avastin (bevacizumab), which is FDA-approved for certain cancers but used off-label for eye conditions. Other anti-VEGF agents include Eylea (aflibercept) and Lucentis (ranibizumab). These injections are typically given every 4 to 8 weeks, depending on the response.
Photodynamic therapy (PDT) is a light-activated treatment that can help reduce subretinal fluid caused by a choroidal nevus. In a small series of 17 cases, one to three sessions of PDT improved average visual acuity from 20/80 to 20/60 (Shields et al., 2023). PDT and anti-VEGF therapy are both considered first-line treatments for nevus-related complications.
If imaging and clinical findings confirm that a nevus has transformed into choroidal melanoma, a retina specialist will refer the patient to an ocular oncologist. Treatment for melanoma of the eye may include radiation therapy, surgical removal, or other specialized approaches. Early detection through regular monitoring gives patients the best chance for successful treatment.
What to Expect
For the vast majority of people, a choroidal nevus is a benign finding that requires no treatment, only periodic monitoring. Most nevi remain stable for decades and cause no vision problems. Knowing that you have a nevus can be reassuring once you understand that monitoring is a precaution, not a sign of a serious problem.
At each monitoring appointment, the retina specialist will dilate your eyes and perform imaging tests. These are compared to previous records. The visit typically takes 30 to 60 minutes. You may experience temporary blurred vision and light sensitivity from the dilating drops for a few hours afterward. Bringing sunglasses and arranging a ride home can make the experience more comfortable.
The long-term outlook for people with a choroidal nevus is very favorable. Because the transformation rate is estimated at only 1 in 9,000 per year (ASRS, 2024), the overwhelming majority of nevi pose no threat to vision or health. Consistent follow-up with a retina specialist ensures that the rare nevus showing signs of change is caught early and managed appropriately.
Living With a Choroidal Nevus
Having a choroidal nevus is a reminder of the importance of regular eye care. Keep all scheduled monitoring appointments, even if your vision feels normal. Report any new visual symptoms to your retina specialist promptly. These include blurriness, distortion, new floaters, or flashes of light.
The direct link between sunlight exposure and choroidal nevus growth is still being studied. However, protecting your eyes from ultraviolet (UV) light is a good practice for overall eye health. Wearing sunglasses that block both UVA and UVB rays when outdoors may reduce the risk of several eye conditions. Maintaining a healthy weight and managing conditions such as high blood pressure may also support long-term eye health.
Learning that you have a spot inside your eye can cause anxiety, especially when words like 'melanoma' are part of the conversation. It is important to remember that a choroidal nevus is comparable to a skin freckle. The vast majority of people with a nevus do not develop melanoma. If you find yourself feeling anxious between monitoring visits, consider discussing your concerns with your retina specialist. Understanding the low statistical risk of transformation can help put your mind at ease.
When to See a Retina Specialist
Adults aged 40 and older should have a comprehensive dilated eye exam as recommended by their eye care provider. If a choroidal nevus is found during a routine exam by an optometrist or general ophthalmologist, a referral to a retina specialist may be appropriate for detailed evaluation and baseline imaging.
Contact a retina specialist or seek emergency care immediately if you experience a sudden increase in floaters, new flashes of light, a dark curtain or shadow moving across your vision, or sudden loss of vision in one eye. These symptoms may indicate a retinal emergency and should not be delayed, regardless of whether you have a known choroidal nevus.
Questions and Answers
A choroidal nevus can, in rare cases, transform into choroidal melanoma. The estimated rate of transformation is approximately 1 in 9,000 per year (ASRS, 2024). The risk increases when specific features are present, such as thickness greater than 2 mm, subretinal fluid, orange pigment, or a diameter greater than 5 mm. Regular monitoring allows a retina specialist to detect any changes at the earliest possible stage.
The monitoring schedule depends on the features of the nevus and the judgment of your retina specialist. A small, low-risk nevus may need to be checked once a year. A nevus with one or more risk features may require more frequent visits, sometimes every 3 to 6 months. Your retina specialist will determine the right schedule based on imaging findings and clinical examination.
Most choroidal nevi do not require any treatment. They are simply monitored over time. Treatment becomes necessary only if the nevus causes complications such as fluid buildup under the retina or abnormal blood vessel growth. In those cases, anti-VEGF injections or photodynamic therapy (PDT) can help manage the complication and protect vision.
No, a choroidal nevus and macular degeneration are different conditions. A choroidal nevus is a collection of pigmented cells in the choroid, similar to a skin mole. Macular degeneration is a progressive condition that damages the macula. However, a nevus located near the macula can sometimes cause changes that resemble features of macular degeneration, such as drusen or fluid buildup. A retina specialist can distinguish between the two conditions using imaging tests.
A choroidal nevus on its own does not mean you are at higher risk for skin melanoma. However, people who have many skin moles or a personal history of skin cancer should mention this to their retina specialist. Both skin moles and choroidal nevi involve melanocytes. Awareness of changes in either area is a reasonable part of overall health monitoring.