Choroidal melanoma is a rare but serious eye cancer that develops in the choroid, the layer of blood vessels between the retina and the outer white wall of the eye. Though uncommon, it stands as the most frequent primary cancer inside the adult eye, often discovered during routine eye examinations before symptoms appear. Understanding this condition helps patients and families navigate diagnosis, treatment choices, and long-term care with greater confidence.
Epidemiology
Choroidal melanoma affects a small portion of the population, but understanding who is most at risk helps with early detection. The incidence of this cancer varies significantly depending on geographic location, ethnicity, and individual characteristics. Global estimates suggest that between five and ten people per million are diagnosed with choroidal melanoma each year, though rates differ by region and population group.[1][2]
In populations of European descent, the incidence ranges from six to seven and a half cases per million annually. Some regions report even higher numbers—the United Kingdom records up to ten cases per million, and Australia reports approximately seven to eight cases per million.[1][7] Notably, Queensland, Australia, which sits beneath the ozone hole, has the highest documented incidence worldwide at ten per million per year, roughly double the rate seen in the United States and Europe.[11]
Choroidal melanoma predominantly affects individuals with lighter skin tones and light-colored eyes such as blue or green. People who are white face a significantly higher risk compared to other racial groups. The condition is slightly more common in men than in women.[1][8] Age also plays a crucial role in the disease’s epidemiology. Most cases are diagnosed in individuals around 55 years of age, with the peak diagnostic age range falling between 70 and 79 years. The approximate median age at diagnosis is 63 years, meaning the disease rarely occurs in younger adults.[1][5]
Within the broader category of uveal melanoma—melanoma that arises from the middle layer of the eye—choroidal melanoma represents the largest subset, accounting for approximately 90 percent of cases. The remaining 5 to 8 percent originate in the ciliary body, the ring of tissue behind the iris that helps the lens focus, and 3 to 5 percent start in the iris, the colored part of the eye.[1] Uveal melanoma as a whole represents about 3 to 5 percent of all melanomas in the body.[1]
Causes
The exact cause of choroidal melanoma remains unclear, but researchers believe it results from a combination of genetic and environmental factors. The cancer begins when cells called melanocytes, which produce the pigment melanin in the choroid, undergo changes in their DNA. These genetic mutations cause the cells to grow and multiply uncontrollably, forming a tumor.[5][8]
Unlike skin melanoma, which has a well-established link to ultraviolet radiation from sun exposure, the connection between sunlight and choroidal melanoma is less direct but still significant. Evidence supporting the role of ultraviolet radiation includes the higher incidence in areas with greater sun exposure, such as Queensland, Australia. Additional clues come from the fact that choroidal melanomas are more frequently found in the posterior, or back, part of the eye, which receives more sunlight exposure. Research also shows that melanomas of the iris occur more often on the lower part, which is more exposed to sunlight entering the eye.[11]
Because the disease is rare and does not run in families in most cases, scientists continue to study how inherited traits and environmental exposures interact to trigger the disease. What is known is that certain inherited characteristics, such as having fair skin and light eyes, increase susceptibility, possibly due to lower levels of protective pigment in the eye and skin.[5]
Risk Factors
Several factors increase the likelihood of developing choroidal melanoma, though having one or more risk factors does not guarantee that the disease will occur. Conversely, some individuals develop the condition without any identifiable risk factors. The strongest and most consistent risk factor is having a fair complexion. This includes fair skin that burns easily, freckles readily, and tans poorly or not at all. People with naturally light-colored eyes—blue, green, or other pale shades—face a higher risk than those with darker eyes.[8][10]
Being unable to tan and experiencing frequent sunburns also elevate risk. These characteristics suggest lower levels of protective melanin, which normally shields tissues from the damaging effects of ultraviolet light. Outdoor occupations that involve prolonged sun exposure have been associated with greater risk, reinforcing the suspected role of environmental factors.[11]
Age is another important risk factor. The condition is extremely rare in children and young adults, with the vast majority of cases occurring after age 50. Older adults, particularly those in their seventh and eighth decades of life, represent the highest-risk group.[1][8] Being white significantly increases the likelihood of developing choroidal melanoma compared to other racial or ethnic groups.[8]
Some individuals have nevi, which are pigmented growths or freckles on or near the eye. While most nevi are benign and never become cancerous, their presence requires monitoring. Similarly, having atypical moles on the skin or a history of freckles may be associated with a slightly increased risk.[5] Genetic mutations that increase susceptibility to certain cancers can also play a role, though this is less common.[5]
Symptoms
One of the most concerning aspects of choroidal melanoma is that it often causes no symptoms in its early stages. Many cases are discovered incidentally during routine eye examinations when an eye care professional looks inside the eye through a dilated pupil. The more forward the tumor originates in the eye, the longer it may take for symptoms to appear, allowing the cancer to grow unnoticed for extended periods.[3][14]
When symptoms do occur, they typically relate to changes in vision. Blurred vision is one of the most common complaints, affecting about 38 percent of patients at the time of diagnosis. This occurs when the tumor disrupts the normal function of the retina, the light-sensing tissue at the back of the eye, or causes fluid to accumulate beneath it.[7][14] Some patients describe seeing flashes of light, a symptom called photopsia, or perceive dark spots or shapes drifting across their field of vision, known as floaters. Floaters are reported by approximately 7 percent of patients and result from changes in the clear gel that fills the center of the eye.[1][7]
Progressive visual field loss is another symptom, where portions of a person’s side or peripheral vision become blocked or go dark. This happens when the tumor grows large enough to interfere with the retina’s ability to process light from certain directions. Some individuals experience distortion in their vision, where straight lines appear wavy or objects seem warped in shape or size—a condition called metamorphopsia.[6][17]
In more advanced cases, patients may notice a growing dark spot on the iris, visible to the naked eye, or a change in the shape or appearance of the pupil. Eye pain is rare unless the tumor has caused complications such as increased pressure inside the eye, leading to a condition called glaucoma, or inflammation within the eye. Severe ocular pain, total loss of vision, or symptoms like a painful blind eye with clouding of the lens (cataract) suggest advanced disease.[3][14]
Sometimes the tumor remains hidden beneath other eye problems, such as a large retinal detachment—when the retina pulls away from its supporting tissue—or bleeding inside the eye. In rare instances, advanced choroidal melanoma can extend through the wall of the eye into the surrounding tissues, causing the eye to bulge forward, a condition known as proptosis.[3][14]
Prevention
Because the precise cause of choroidal melanoma is not fully understood, definitive prevention strategies remain limited. However, taking steps to protect the eyes from ultraviolet radiation may help reduce risk, particularly for individuals with fair skin and light-colored eyes who are at higher risk. Wearing high-quality sunglasses that block both UVA and UVB rays is a simple and effective measure. Sunglasses should be worn whenever spending time outdoors, especially during peak sunlight hours or in environments with intense sun exposure, such as beaches or high altitudes.[11]
Wide-brimmed hats provide additional protection by shading the eyes from direct sunlight. For people who work outdoors or engage in outdoor recreational activities frequently, combining sunglasses with hats offers the best defense. These measures are not guaranteed to prevent choroidal melanoma, but they align with broader eye health recommendations and may lower overall risk.[11]
Regular eye examinations are crucial, particularly for individuals at higher risk. While these exams cannot prevent the disease, they enable early detection when the tumor is smaller and more treatable. Eye care professionals can identify suspicious lesions, such as pigmented nevi, and monitor them over time for signs of growth or change. Early diagnosis significantly improves treatment outcomes and may help preserve vision and the eye itself.[7][15]
For individuals with atypical moles or nevi in or around the eye, close surveillance is recommended. These growths should be photographed and measured regularly to detect any increase in size, which may indicate transformation into melanoma. Promptly reporting any changes in vision or appearance of the eye to a healthcare provider is also important.[5]
Maintaining overall health through a balanced diet, regular physical activity, and avoidance of smoking supports the immune system and general well-being, though no specific dietary or lifestyle intervention has been proven to prevent choroidal melanoma. Genetic counseling may be considered for individuals with a family history of cancer or known genetic mutations that increase cancer risk, though hereditary cases of choroidal melanoma are uncommon.[5]
Pathophysiology
Understanding the changes that occur in the body when choroidal melanoma develops helps clarify how the disease affects vision and overall health. The choroid is a thin layer of tissue located between the sclera, the white outer wall of the eye, and the retina, the light-sensitive inner lining. It is rich in blood vessels that supply oxygen and nutrients to the retina and other parts of the eye. This vascular network is essential for maintaining normal eye function.[1][15]
Choroidal melanoma arises when melanocytes in the choroid undergo genetic mutations and begin to multiply uncontrollably. As the tumor grows, it forms a mass that can take various shapes. Small tumors typically appear as dome-shaped, well-defined lumps beneath the retinal pigment epithelium, the layer of cells that supports the retina. As the tumor enlarges, it may adopt irregular shapes, including bilobular (two-lobed), multilobular (many-lobed), or mushroom-like configurations.[3][14]
The tumor’s color can vary widely, ranging from completely lacking pigment (amelanotic) to partially pigmented to deeply dark. If the tumor is light in color, its abnormal network of blood vessels may be visible during examination. Overlying the melanoma, changes often occur in the retinal pigment epithelium, including the formation of small yellow deposits called drusen, patches where the tissue has wasted away (atrophy), and orange discoloration caused by lipofuscin, a byproduct of dying cells.[2][3][14]
As the tumor expands, it can disrupt the normal architecture of the eye in several ways. It may press against the retina, interfering with its ability to detect light and transmit visual signals to the brain, leading to blurred or distorted vision. The tumor’s abnormal blood vessels are often poorly formed and leaky, causing fluid to accumulate beneath the retina in a condition called subretinal fluid. Large amounts of this fluid can lead to retinal detachment, where the retina lifts away from its supporting layers. This detachment blocks light from reaching the retina and causes significant vision loss.[2][17]
In some cases, the tumor grows outward and penetrates through the sclera into the tissues surrounding the eye, a situation called extraocular extension. This extension represents a more advanced stage of disease and complicates treatment. The tumor may also cause secondary complications such as bleeding inside the eye (vitreous hemorrhage) or increased pressure within the eye, leading to glaucoma. These complications can cause pain and further vision impairment.[3][14]
The most serious aspect of choroidal melanoma’s pathophysiology is its potential to spread beyond the eye to other parts of the body, a process known as metastasis. Uveal melanomas, including choroidal melanomas, have a particular tendency to spread to the liver. Approximately 50 percent of patients with choroidal melanoma will develop metastatic disease despite receiving treatment and careful monitoring. Once the cancer has spread, it becomes much more difficult to treat and significantly affects survival.[1][7] The median survival for individuals with metastatic disease is short, emphasizing the importance of early detection and treatment to prevent or delay metastasis.[7]
Several factors influence the tumor’s behavior and prognosis. The size and thickness of the tumor are critical—larger and thicker tumors are more likely to grow aggressively and spread. The type of cells that make up the tumor also matters. Melanomas composed primarily of spindle-shaped cells (spindle cells) generally have a better prognosis than those made up of round epithelioid cells or a mix of both cell types. Genetic features of the tumor, such as specific mutations, can also predict how the cancer will behave and respond to treatment.[1][23]
