A choroidal nevus is a flat or slightly raised cluster of pigmented cells inside the eye, sitting in the choroid layer beneath the retina. Think of it as a freckle on the back of your eye. Roughly one in twenty U.S. adults over 40 has one, and the vast majority never cause symptoms or require treatment. The concern that brings most people to search this term, though, is the question of cancer, and the short version is reassuring: the annual rate of any single choroidal nevus transforming into melanoma is estimated at about 1 in 8,845. But that tiny risk is not zero, and the way eye specialists monitor these spots has become remarkably sophisticated.
How Common Are Choroidal Nevi
Prevalence estimates depend on which population is studied and how the eye is examined. A nationally representative U.S. survey found that about 4.7% of adults aged 40 and older had a choroidal nevus visible in the posterior portion of the eye, with the rate climbing steadily by decade: roughly 3% in people in their 50s, 5% in those in their 60s, and 7–8% in those 80 and above.1PubMed. Choroidal Nevus in the United States Adult Population: Racial Disparities and Associated Factors in the National Health and Nutrition Examination Survey An Australian study using a slightly different photographic method reported a prevalence of 6.5% in a predominantly white cohort, with over 90% of affected people having a nevus in just one eye.2JAMA Ophthalmology. Choroidal Nevi in a White Population: The Blue Mountains Eye Study The 5% ballpark that eye specialists commonly cite for U.S. adults is a reasonable middle ground.3PubMed. Choroidal nevus: a review of prevalence, features, genetics, risks, and outcomes
Race plays a notable role. The Multi-Ethnic Study of Atherosclerosis found the overall prevalence to be about 2.1% across its entire multi-ethnic cohort, but when broken down by group, 4.1% of white participants had a nevus compared with 1.2% of Hispanic participants, 0.7% of Black participants, and 0.4% of Chinese participants.4PubMed Central. Prevalence and characteristics of choroidal nevi: the multi-ethnic study of atherosclerosis This mirrors what dermatologists see with skin moles: lighter pigmentation tends to come with more melanocytic lesions.
What a Choroidal Nevus Looks Like
Your eye doctor usually spots a choroidal nevus during a dilated eye exam as a gray, brown, or slate-colored flat patch on the retinal surface. Under the microscope, these lesions are made up of plump or spindle-shaped pigmented cells with little abnormal activity.5PubMed Central. What’s in a Name? Large Choroidal Nevus, Small Choroidal Melanoma, or Indeterminate Melanocytic Tumor Most sit in the back half of the eye; in the Australian study, about half of all nevi were within the posterior pole, and roughly 85% lay on the temporal (ear-ward) side of the optic disc.6JAMA Ophthalmology. Choroidal Nevi in a White Population: The Blue Mountains Eye Study
A study of over 2,500 consecutive nevus cases documented several features that commonly accompany the lesion. Drusen, tiny yellowish deposits of debris, were the most common associated finding, seen overlying about half of nevi. Subretinal fluid was present in about 11%, orange pigment (lipofuscin) in about 8%, and changes to the retinal pigment epithelium (the cell layer just above the nevus) in roughly 8–11%, depending on the type of change.7Archives of Ophthalmology. Choroidal Nevus Transformation Into Melanoma: Analysis of 2514 Consecutive Cases Many of these features are harmless and simply reflect the nevus sitting there for years, but some of them, as we will see, factor into melanoma risk assessment.
The Melanoma Question
The single biggest worry patients have when told “you have a freckle in your eye” is whether it could become cancer. The numbers are overwhelmingly in your favor. One widely cited estimate puts the annual rate of any given nevus transforming into melanoma at roughly 1 in 8,845, based on comparing U.S. melanoma incidence with estimates of how many nevi exist in the adult population.8PubMed. Estimating the risk of malignant transformation of a choroidal nevus To put that in everyday terms, if you followed a thousand people with a nevus for ten years, the vast majority would see no change at all.
Still, choroidal melanoma is the most common primary eye cancer in adults, and catching it early dramatically improves outcomes. So eye specialists have developed a structured way to gauge how suspicious a given nevus looks.
How Specialists Assess Risk
The most widely used framework comes from a longitudinal study of over 2,300 nevi tracked with multiple imaging methods. Researchers identified six features that predict growth toward melanoma, remembered by the mnemonic TFSOM-DIM (“To Find Small Ocular Melanoma Doing Imaging”):
- Thickness: greater than 2 mm on ultrasound
- Fluid: subretinal fluid visible on OCT scanning
- Symptoms: vision loss to 20/50 or worse
- Orange pigment: lipofuscin detected on autofluorescence imaging
- Melanoma hollow: acoustic hollowness on ultrasound
- Diameter: greater than 5 mm on fundus photography
The power of the system is in how sharply risk climbs with each added factor. A nevus with none of these features carries roughly a 1% chance of growth over five years. With any one factor present, the five-year risk jumps to about 11%. Two factors push it to about 22%, three to 34%, and five factors to around 55%.9PubMed. Understanding choroidal nevus risk factors for transformation into melanoma In multivariate analysis, thickness above 2 mm carried the highest hazard, nearly quadrupling the risk of transformation.10Retina. Choroidal Nevus Imaging Features in 3,806 Cases and Risk Factors for Transformation Into Melanoma in 2,355 Cases
A separate scoring system called MOLES has been introduced more recently, designed to help community optometrists triage which patients need urgent referral to an ocular oncologist and which can be monitored locally. Under this framework, common low-risk nevi can be followed by your regular optometrist at routine visits, while higher-risk lesions get referred for specialized imaging and closer surveillance.11Eye. Can the MOLES acronym and scoring system improve the management of patients with melanocytic choroidal tumours? The practical takeaway: if your eye doctor tells you a nevus is low-risk and to come back in a year, that is standard care, not negligence.
What Modern Imaging Reveals
Three imaging technologies do most of the heavy lifting in nevus monitoring. Optical coherence tomography (OCT) creates cross-sectional images of the retina at near-microscopic resolution. In a study of 120 nevus patients, OCT showed that the overlying retina was thickened in about 45% of cases, thinned in 22%, and normal in the remaining third, with about half showing some photoreceptor loss or thinning.12Retina. Optical coherence tomography of choroidal nevus in 120 patients Enhanced-depth OCT can see even deeper, revealing changes like thinning of the blood vessel layer (choriocapillaris) directly overlying the nevus, which was found in 94% of cases in one series.13PubMed. Enhanced depth imaging optical coherence tomography of choroidal nevus in 104 cases
Fundus autofluorescence imaging detects lipofuscin, a metabolic waste product that lights up on the scan. This matters because prominent lipofuscin over a choroidal lesion is one of the TFSOM-DIM warning signs. Encouragingly, most nevi lack characteristic autofluorescence, while melanomas tend to show a distinctive pattern of bright, confluent signal.14PubMed Central. Fundus autofluorescence of choroidal nevus and melanoma The third tool, B-scan ultrasonography, measures thickness and checks for internal hollowness, both key items on the risk checklist.
Enhanced-depth OCT has also sharpened the ability to distinguish nevi from other pigmented lesions in the eye. On imaging, a typical nevus appears as a smooth, moderately dome-shaped mass with overlying retinal pigment changes, which looks quite different from, say, a choroidal hemangioma (which tends to be more steeply dome-shaped with fluid accumulation) or congenital hypertrophy of the retinal pigment epithelium (which is flat).15RETINA. Enhanced Depth Imaging Optical Coherence Tomography of Intraocular Tumors
Genetics Behind the Freckle
One of the more striking findings in recent years is that choroidal nevi carry many of the same gene mutations found in full-blown uveal melanoma. A study using sensitive DNA detection found that 15 out of 16 nevi harbored a mutation in either the GNAQ or GNA11 gene, which are the driver mutations in the vast majority of uveal melanomas.16PubMed Central. GNAQ and GNA11 mutations and downstream YAP activation in choroidal nevi The fraction of cells carrying the mutation varied widely, from just 1% to 55%, with a median around 13%.17British Journal of Cancer. GNAQ and GNA11 mutations and downstream YAP activation in choroidal nevi
This shared genetic starting point tells us that a nevus and a melanoma begin life in a similar way, with the same initial mutation kicking cells into overdrive. What keeps most nevi from becoming cancers appears to be the absence of additional mutations that would disable the cell’s growth brakes. In practical terms, having one of these driver mutations does not make a nevus dangerous on its own; it simply explains why the pigmented cells proliferated in the first place. The rarity of transformation suggests that the second and third genetic hits needed for malignancy are uncommon events.
When a Nevus Causes Vision Problems
Most choroidal nevi are completely silent. You have no way of knowing one is there unless an eye doctor looks. But in a small number of cases, a nevus sitting near the center of the retina can cause real visual trouble, not through cancer but through a complication called choroidal neovascularization (CNV), where abnormal new blood vessels sprout from or near the nevus.
These new vessels leak fluid and blood beneath the retina, leading to distorted or blurry central vision. The complication is rare but well documented. Case reports and small series describe successful treatment with injections of anti-VEGF drugs (the same medications used for age-related macular degeneration) directly into the eye. In one series of 10 patients with CNV overlying a chronic nevus, most had fluid beneath the fovea, the spot responsible for sharp central vision, and several also had hemorrhage or fatty deposits.18Retina. Intravitreal Bevacizumab for Choroidal Neovascularization Associated with Choroidal Nevus Newer imaging with OCT angiography can detect these abnormal vessels without injecting dye, making it easier to catch the problem early.19PubMed Central. Choroidal Nevus-Associated Neovascular Membrane Demonstrated by OCT Angiography
A separate situation arises when a nevus produces subretinal fluid that pools under the fovea, causing vision loss even without new blood vessels. A recent small study explored photodynamic therapy (a light-activated laser treatment) for this specific scenario and found that six of seven treated eyes responded within a month, with fluid mostly resolving. However, half of those responders saw the fluid return within about nine months, suggesting the treatment may need to be repeated.20PubMed Central. Clinical Outcomes of Photodynamic Therapy for Choroidal Nevus with Subfoveal Fluid These are niche situations, but they are worth knowing about because they represent the rare instances where a benign nevus can genuinely interfere with daily life.
Choroidal Nevi in Children
Nevi are much less common in kids than in adults, but they do occur. A study screening over 5,500 children found a prevalence of less than 0.5% in those under six, rising to about 1.8% by age 18, consistent with the idea that nevi accumulate with age even in youth.21PubMed. Choroidal nevi in children: prevalence, age of onset, and progression The lesions in children tended to be small, averaging about 1.6 mm across, and none showed the secondary changes like drusen or orange pigment that adults commonly have. Among children who were followed over time, the majority of nevi remained stable, and no malignant transformation was observed in that cohort.
A separate pediatric imaging study of 79 patients (mean age 12) provided a longer view. Over an average follow-up of nearly four years, two nevi out of 85 did transform into melanoma, both at roughly the four-year mark. Acoustic hollowness on ultrasound was strongly associated with those transformations. Separately, four nevi grew without becoming malignant, and all four of those growth episodes happened during puberty, raising the possibility that hormonal changes can spur benign enlargement.22Investigative Ophthalmology & Visual Science. Clinical Features and Multimodal Imaging Characteristics of Choroidal Nevi in Pediatric Patients For parents, the message is that pediatric choroidal nevi are uncommon and overwhelmingly benign, but they still warrant periodic monitoring, especially through adolescence.
Eye Color, Skin Moles, and Wider Risk Factors
If you have light-colored eyes, you may already know your risk for uveal melanoma is slightly elevated. An Australian case-control study quantified this: people with grey eyes had about three times the odds of developing choroidal or ciliary body melanoma compared with brown-eyed individuals, and those with hazel or blue eyes also faced increased risk. The same study found that having four or more moles on the back, being unable to tan, and habitual squinting outdoors as a child were all independent risk factors.23PubMed. Eye color and cutaneous nevi predict risk of ocular melanoma in Australia The link between skin moles and eye lesions is not fully understood, but it hints that some broader genetic predisposition to melanocytic proliferation operates across tissues.
Whether choroidal nevi run in families is harder to pin down. One genetic study of families with uveal melanoma found choroidal nevi in some siblings of affected patients, suggesting a familial clustering.24PubMed. Genetic study of familial uveal melanoma: association of uveal and cutaneous melanoma with cutaneous and ocular nevi But an earlier investigation looking at families with the dysplastic nevus syndrome (a condition marked by many atypical skin moles and high melanoma risk) found no unusual ocular findings, leading those authors to suggest the overlap might be coincidental.25PubMed. The familial occurrence of cutaneous melanoma, intraocular melanoma, and the dysplastic nevus syndrome The evidence remains thin and somewhat contradictory on hereditary patterns.
Artificial Intelligence in Nevus Screening
One emerging development worth watching is the use of AI to help classify choroidal lesions from standard eye photographs. A deep learning algorithm trained on fundus images achieved 100% sensitivity and 74% specificity for distinguishing small melanomas from nevi in a test set, and its overall performance (measured by area under the curve) outperformed clinicians using either the MOLES or TFSOM-DIM scoring systems on the same images.26Ophthalmology Science. Development and Validation of a Deep Learning Algorithm for Differentiation of Choroidal Nevi from Small Melanoma in Fundus Photographs Separate work has tested image-classification models for simply detecting whether a nevus is present and segmenting its boundaries, with ensemble approaches showing the strongest results.27PubMed. Artificial intelligence in the classification and segmentation of fundus images with choroidal nevi
These tools are still in the validation stage and not yet in widespread clinical use, but the trajectory suggests that within the next several years, an AI layer could sit between routine retinal photos taken at a neighborhood optometrist’s office and the decision to refer a patient for specialist evaluation. The potential upside is catching suspicious lesions sooner while sparing low-risk patients unnecessary worry and referrals. For now, the standard practice remains human expert review supplemented by multimodal imaging, but the gap between AI research performance and real-world clinical deployment is narrowing quickly.
Living with a Choroidal Nevus
If you have just been told you have a choroidal nevus, the most practical thing to know is what your follow-up schedule should look like. For a small, flat, low-risk nevus with no TFSOM-DIM warning features, many specialists will photograph the lesion, give you a baseline record, and ask you to return in six to twelve months. If nothing changes, follow-up intervals often lengthen to every one or two years, and monitoring can eventually be done by a community optometrist who compares current images against the baseline. Your job is to keep those appointments and report any new visual symptoms, particularly a noticeable shadow, distortion of straight lines, or a change in sharpness, between visits.
The emotional weight of the diagnosis can be disproportionate to the medical risk. Being told you have something in your eye that could theoretically become cancer understandably generates anxiety, even when the numbers are strongly in your favor. Asking your eye doctor to show you the photograph of the lesion and walk you through the risk factors can help demystify what you are dealing with. A freckle with no warning features is, statistically, just a freckle that happens to be inside your eye rather than on your arm.