Choroidal Nevus

A choroidal nevus is a flat or slightly raised pigmented spot in the choroid—the layer of blood vessels and pigment that lies just behind the retina inside the eye. It is commonly called an eye freckle. Like a skin freckle or mole, a choroidal nevus is made up of melanin-bearing cells (melanocytes) and is almost always entirely harmless and stable throughout a person’s life. Most people who have one never know it, because the nevus causes no symptoms and is discovered incidentally during a routine dilated eye examination. The word choroidal refers to the choroid layer; nevus is a Latin word meaning birthmark or mole.

Choroidal nevi are the most common primary intraocular (inside the eye) tumors encountered in clinical practice. Population estimates vary by detection method—studies using dilated eye exams suggest that between 5 and 25% of adults have at least one choroidal nevus, while photographic studies of the posterior eye document a prevalence of 2–6%. The wide range reflects differences in examination technique and population studied. Nevi are more common in people with lighter skin and eye pigmentation.

The vast majority of choroidal nevi remain completely stable and never cause any harm. However, there are two clinical risks to be aware of: first, if a nevus is located directly under the center of the retina (the fovea), it can occasionally cause some vision disturbance; second, a very small number of choroidal nevi—roughly 1 in 8,000 per year among all adults who carry one—transform into choroidal melanoma, a malignant tumor. Because this risk exists, choroidal nevi are monitored with periodic dilated eye examinations and, in higher-risk cases, with imaging. The goal of monitoring is to catch any sign of growth or malignant change early, when intervention is most effective.

Ophthalmologists classify choroidal nevi by their pigmentation, their size and location within the eye, and their risk profile—particularly whether specific features associated with a higher chance of growth are present.

• Melanotic (pigmented) nevus: the most common type, present in 84–97% of cases. It appears as a slate-gray, blue-green, or brown spot under the retina. It is composed of melanin-bearing spindle cells, the same cell type as a benign skin mole.
• Amelanotic (nonpigmented) nevus: lacks melanin pigment and appears pale or tan rather than dark. It accounts for about 7% of choroidal nevi and is diagnostically more challenging because its lack of pigment can resemble other conditions, such as a choroidal hemangioma or a metastatic tumor.
• Mixed pigmentation nevus: contains both pigmented and non-pigmented areas and makes up about 9% of cases. It presents an intermediate diagnostic challenge.
• Low-risk (typical) nevus: a nevus with features that indicate it has been stable and benign for a long time. These favorable features include overlying drusen (small, yellowish calcium deposits on the retinal surface above the nevus), changes to the retinal pigment epithelium (a thin supportive cell layer above the choroid), and a pale halo of depigmentation around the lesion. Their presence is reassuring and suggests a very low risk of malignant change.
• High-risk (atypical) nevus: a nevus with one or more features that are associated with a meaningfully higher probability of growth or malignant transformation. These risk factors are assessed using a validated system called TFSOM-DIM (described in the Diagnosing section below). The presence of multiple risk factors requires more frequent monitoring and, in some cases, referral for treatment.
• Indeterminate melanocytic tumor: a lesion at the clinical boundary between a large choroidal nevus and a small choroidal melanoma. This is a recognized diagnostic category that requires biopsy or very close surveillance because the distinction cannot always be made on imaging alone.
• Choroidal melanocytoma: a variant of choroidal nevus that is deeply, intensely pigmented—often jet-black in appearance. Unlike typical nevi, melanocytomas occur equally across all racial and ethnic groups. They can slowly enlarge and rarely undergo malignant transformation, but they require regular monitoring.

Choroidal nevi arise from melanocytes—pigment-producing cells that are normally distributed throughout the choroidal layer of the eye. These cells are derived embryologically from the neural crest, the same cell lineage that gives rise to skin melanocytes and other pigmented tissues throughout the body. Most choroidal nevi are thought to be congenital in origin, meaning the cluster of abnormal melanocytes that forms the nevus develops before or shortly after birth, even though the nevus itself may not be detected until adulthood.

The specific trigger that causes a group of choroidal melanocytes to cluster and form a nevus is not fully understood. Genetic factors are likely important—nevi are more common in people of lighter complexion and in those with a family history of uveal nevi or melanoma, suggesting inherited susceptibility involving genes that regulate melanocyte proliferation. Somatic (noninherited) mutations in the GNAQ and GNA11 genes—the same genes mutated in uveal melanoma—have been identified in a proportion of benign choroidal nevi, suggesting that these early mutations drive the initial formation of the nevus but are insufficient on their own to cause malignant transformation. Additional mutations must accumulate for a nevus to become malignant. Unlike skin melanoma, ultraviolet radiation has not been clearly established as a cause of choroidal nevi, because the choroid is largely shielded from ultraviolet (UV) light by the pigmented tissues in front of it.

The following factors are associated with the presence of choroidal nevi and, separately, with the risk of a nevus transforming into a malignant tumor.

• Light skin and eye color: Choroidal nevi are more commonly found in people of northern European descent and in those with lighter iris pigmentation (blue or green eyes). They are less common in people of African and Asian ancestry.
• Age: The prevalence of choroidal nevi increases with age, as lesions that have been present since birth or childhood become more readily detectable on examination.
• Family history: A family history of choroidal nevus, uveal melanoma, or dysplastic nevus syndrome (a condition involving many atypical skin moles) is associated with higher individual risk.
• BAP1 tumor predisposition syndrome: A rare inherited condition caused by a mutation in the BAP1 gene dramatically increases the risk of uveal melanoma, mesothelioma, and other cancers. People with this syndrome may develop multiple ocular melanocytic lesions.
• Risk factors for transformation to melanoma: Several features of the nevus itself—rather than patient demographics—are the strongest predictors of malignant change. These are assessed with the TFSOM-DIM system and include greater thickness, subretinal fluid, symptoms, orange pigment, acoustic hollowness on ultrasound, larger diameter, and proximity to the optic nerve. The more of these features present, the higher the risk of growth and transformation.

There is no population-level screening program specifically for choroidal nevi. They are almost universally discovered incidentally during routine dilated fundus examinations performed by an ophthalmologist or optometrist for an unrelated reason—such as a general check-up, monitoring for diabetes or glaucoma, or a new glasses prescription. The fact that 87–88% of patients are completely asymptomatic at the time of discovery underscores the importance of regular comprehensive dilated eye exams as the primary vehicle for detection.

Choroidal nevi cannot be prevented, as they arise from the normal developmental distribution of melanocytes in the choroid. Prevention of malignant transformation—the more clinically important goal—is not yet possible because we cannot predict with certainty which nevi will transform, and we do not have a proven intervention that prevents transformation before it occurs. The most effective management strategy is early detection through routine eye care and consistent follow-up monitoring once a nevus has been identified. Adults over age 40 should have a dilated eye exam at least every one to two years. Those with known choroidal nevi should follow the monitoring schedule recommended by their eye doctor based on the risk profile of their specific lesion.

The vast majority of choroidal nevi—87–88%—cause no symptoms at all. They are found by a doctor during a dilated eye examination when the patient has come in for a completely unrelated reason. Most people with a choroidal nevus never experience any visual symptoms throughout their lives.

When symptoms do occur, they are typically caused by the nevus’s location or by secondary changes it has produced in the overlying retinal tissue. Possible symptoms include:

• Blurred or distorted central vision: When the nevus is located directly under or adjacent to the fovea (the center of the macula, responsible for sharp, detailed vision used for reading and recognizing faces), it can distort the retinal surface and impair central vision.
• Visual field defect: This may present as a small scotoma (blind spot) or shadow in the visual field, corresponding to the location of the nevus.
• Photopsia: This refers to flashes of light, which can occur when the nevus causes traction (pulling) on the overlying retinal tissue.
• Metamorphopsia: Straight lines appear wavy or bent, caused by fluid accumulation under or within the retina above a leaking or growing nevus.
• Reduced color vision or contrast sensitivity: This is less common and may reflect involvement of the overlying cone photoreceptors in the central macula.

Any of these symptoms in a person known to have a choroidal nevus should prompt an immediate visit to their eye doctor for re-evaluation, as new symptoms may indicate a change in the lesion. The development of new symptoms—particularly new visual distortion, worsening central vision, or new floaters—alongside a known choroidal nevus should be evaluated without delay.

Choroidal nevi are diagnosed by an ophthalmologist during a comprehensive dilated eye examination. The key diagnostic challenge is distinguishing a benign choroidal nevus—which requires only periodic monitoring—from a growing or potentially malignant lesion that requires more urgent evaluation and treatment. This distinction is made through a combination of clinical examination, multimodal imaging, and systematic risk assessment.

• Dilated fundus examination: The doctor dilates the pupil with eye drops and examines the back of the eye using a lens and light. This allows direct visualization of the choroidal nevus, its color, shape, borders, and any surface changes such as drusen or orange pigment.
• Fundus photography: High-resolution color photographs of the retina document the lesion precisely and serve as a baseline for comparison at future visits. Any change in size, shape, or pigmentation over time is easily detected by comparing serial photographs.
• Optical coherence tomography (OCT): a noninvasive scan that produces cross-sectional images of the retinal layers above and around the nevus. It detects subretinal fluid (fluid under the retina), retinal edema, photoreceptor damage, and changes at the level of the retinal pigment epithelium. Subretinal fluid detected on OCT is one of the strongest risk factors for growth and malignant transformation.
• B-scan ultrasonography: a sound-wave-based imaging test that measures the thickness of the choroidal lesion and assesses its internal acoustic character. Acoustic hollowness (low internal reflectivity, meaning sound waves pass through the lesion with little reflection) is a risk factor for malignancy. B-scan is particularly important for measuring lesion thickness precisely, as thickness is a key factor in risk stratification.
• Fundus autofluorescence (FAF): a specialized imaging technique that detects lipofuscin, the metabolic byproduct that accumulates as orange pigment on the surface of some choroidal nevi. Orange pigment (lipofuscin) is a significant risk factor for malignant transformation and is best seen on autofluorescence imaging.
• Fluorescein and indocyanine green (ICG) angiography: dye-based imaging studies that evaluate the blood vessels within and around the choroidal nevus, detect leakage, and characterize the lesion’s vascular pattern. These are used selectively when the diagnosis is uncertain or when treatment for a complication such as choroidal neovascularization is being planned.
• TFSOM-DIM risk assessment: a validated clinical scoring system that uses seven specific risk factors to estimate the probability of malignant transformation. The acronym stands for: Thickness (greater than 2 mm), subretinal Fluid (present on OCT), Symptoms (any visual symptoms), Orange pigment (lipofuscin on autofluorescence), Melanoma hollowness (acoustic hollowness on B-scan), tumor DIaMeter (greater than 5 mm). Each factor present confers additional risk: with zero factors, the five-year risk of transformation is approximately 1%; with three or more factors, the risk rises to 34% or higher. This scoring system guides the frequency of monitoring and the threshold for intervention.

The great majority of choroidal nevi require no treatment—only careful, consistent monitoring. The management approach is individualized based on the nevus’s risk profile as determined by the TFSOM-DIM assessment and the patient’s overall eye health. Your ophthalmologist will establish the right monitoring schedule and discuss the findings at each visit.

For low-risk typical nevi—those with benign features such as overlying drusen and retinal pigment epithelium (RPE) changes, no subretinal fluid, no orange pigment, small size, and no associated symptoms—observation is the standard of care. The recommended monitoring schedule typically involves a dilated eye examination and fundus photography at six to twelve months after the initial finding to establish a stable baseline, then annually or every two years if stability is confirmed. Multimodal imaging (OCT, autofluorescence) is incorporated into these visits to detect any early changes before they become clinically visible on standard examination.

For nevi with one or more high-risk TFSOM-DIM features, monitoring is more frequent—typically every three to six months—and the threshold for referral to a specialist in ocular oncology (a physician who specializes in eye tumors) is lower. When a nevus is borderline, and the distinction between a large nevus and a small choroidal melanoma cannot be made confidently on imaging alone, fine-needle aspiration biopsy (FNAB) of the lesion—a minimally invasive procedure performed through the eye wall—can provide a tissue sample for cytological (cell-type) analysis and genetic testing. Genetic analysis of the biopsy specimen using chromosomal copy number analysis or gene expression profiling can classify the lesion and estimate the risk of metastasis with high accuracy.

When a choroidal nevus develops a complication—most commonly subretinal fluid that threatens central vision or choroidal neovascularization (abnormal blood vessel growth under the retina)—treatment is directed at the complication rather than the nevus itself. Anti-vascular endothelial growth factor (VEGF) injections (such as bevacizumab or ranibizumab) administered directly into the vitreous cavity of the eye are used to treat choroidal neovascularization associated with the nevus. Photodynamic therapy (PDT)—a laser-activated treatment using a light-sensitive drug (verteporfin)—may be used for persistent subretinal fluid or neovascularization that does not respond to anti-VEGF therapy. When a choroidal nevus has grown sufficiently to be reclassified as a small choroidal melanoma, treatment options for uveal melanoma are employed: plaque brachytherapy (a radioactive plaque sutured temporarily to the outside of the eye wall to irradiate the tumor from the inside) is the most commonly used treatment for small to medium uveal melanomas and preserves the eye in the majority of cases. Proton beam radiation, transpupillary thermotherapy (TTT), and in some cases surgical resection or enucleation (removal of the eye) are reserved for specific situations depending on tumor size, location, and response.

For the vast majority of people who have a choroidal nevus, the diagnosis is reassuring rather than alarming. An eye freckle is a common finding, and the overwhelming likelihood is that it will remain entirely stable and never cause any problem. The most important thing a person with a choroidal nevus can do is attend their scheduled follow-up appointments consistently. Skipping monitoring visits—particularly in the first one to two years after discovery, when baseline stability is being established—is the main avoidable risk. If any new visual symptoms develop between scheduled visits, calling your eye doctor promptly rather than waiting is the right approach. Visual symptoms alongside a known choroidal nevus should always be evaluated without delay. With regular monitoring and the excellent diagnostic tools available today, any meaningful change in a choroidal nevus can be detected early, giving the best possible chance for successful intervention if it is ever needed.

To further your understanding of your diagnosis and to contribute to cutting-edge research, consider participating in a clinical trial so clinicians and scientists can learn more about causes, symptoms, treatment, and prevention of choroidal nevus and related disorders. Clinical research uses human volunteers to help researchers learn more about a disorder and perhaps find better ways to safely detect, treat, or prevent disease.

All types of volunteers are needed—those who are healthy or may have an illness or disease—of all different ages, sexes, races, and ethnicities to ensure that study results apply to as many people as possible, and that treatments will be safe and effective for everyone who will use them.