Eye cancer has no single cause. It develops when cells in or around the eye accumulate genetic changes that let them grow unchecked. About 3,200 new cases of primary eye cancer are diagnosed in the United States each year, and the specific triggers depend on which type of eye cancer is involved. Some forms trace back to inherited gene mutations present from birth, while others arise from environmental exposures, immune system problems, or cancers that started elsewhere in the body.
How Primary Eye Cancer Starts
The most common primary eye cancer in adults is uveal melanoma, which forms in the pigmented cells of the eye’s middle layer (the uvea). In 80 to 90 percent of these tumors, one of two closely related genes is mutated. These genes normally produce signaling proteins that tell cells when to grow and when to stop. When either gene is mutated, the “off switch” breaks. The protein stays permanently active, flooding the cell with growth signals through multiple pathways that drive cell division.
These mutations are almost always acquired during a person’s lifetime rather than inherited. They tend to occur in a mutually exclusive pattern, meaning a tumor typically carries one or the other but not both. The result is the same either way: the cell loses its ability to regulate its own growth cycle and begins dividing without restraint.
Inherited Genetic Risk
A small but significant portion of eye cancers have a hereditary component. The clearest example is retinoblastoma, a cancer that develops in the retinas of young children. Between 25 and 35 percent of retinoblastoma cases are hereditary, caused by an inherited mutation in a tumor suppressor gene called RB1. This gene produces a protein that normally acts as a brake on cell division. Children who inherit one faulty copy of RB1 need only one additional mutation in the other copy for a tumor to form, which is why hereditary retinoblastoma often appears in both eyes and at a very young age. The remaining 65 to 75 percent of cases are sporadic, meaning both copies of RB1 are damaged by random mutations after birth.
In adults, a condition called BAP1 tumor predisposition syndrome raises the risk of uveal melanoma along with several other cancers, including mesothelioma and kidney cancer. Uveal melanoma is the most frequently reported cancer in people with this syndrome, accounting for 36 percent of those initially diagnosed. It can appear as early as age 16. Among all uveal melanoma patients, only 1 to 2 percent carry this inherited mutation. But among those with a family history of eye melanoma, the rate jumps to 20 to 30 percent.
UV Radiation and Sunlight
The relationship between sunlight and eye cancer is more complicated than many people assume. A large U.S. study covering nearly two decades found that ambient ultraviolet radiation was not associated with an overall increase in ocular melanoma. However, the picture differed depending on which part of the eye was affected. People living in the highest UV exposure areas had a 63 percent higher incidence of melanoma in the iris and ciliary body (the structures at the front of the eye’s interior). This elevated risk appeared only in non-Hispanic White individuals. Paradoxically, choroidal melanoma, which forms in the back of the eye, was actually less common in high-UV areas.
So UV exposure likely plays a role in certain eye cancers but not all of them. The front-of-eye structures receive more direct sunlight, which may explain why they’re more vulnerable.
Occupational and Industrial Exposures
Workers exposed to intense artificial UV radiation face a documented risk. In 2017, the International Agency for Research on Cancer classified UV radiation from welding as carcinogenic to humans, based on sufficient evidence linking it to ocular melanoma. Welders receive concentrated bursts of UV light at close range, often over years or decades. This exposure can damage DNA in eye cells in ways that accumulate over time, similar to how repeated sunburns increase the risk of skin cancer.
Immune Suppression and Viral Infections
Primary intraocular lymphoma, a rarer form of eye cancer, is strongly tied to immune system health. This cancer is a form of lymphoma that develops inside the eye, and it occurs in up to 20 percent of people with primary central nervous system lymphoma.
HIV infection substantially raises the risk. The virus weakens the immune system’s ability to detect and destroy abnormal cells, a process called immune surveillance. As immune defenses decline, Epstein-Barr virus (EBV), which lies dormant in most people, can drive unchecked growth of certain white blood cells. In HIV-positive patients, these lymphomas tend to appear late in the course of infection and show EBV involvement in virtually 100 percent of cases. The combination of weakened immune monitoring and active viral stimulation creates conditions where lymphoma cells can proliferate inside the eye.
People on long-term immunosuppressive drugs, such as organ transplant recipients, face a similar dynamic. Reduced immune function allows EBV to act with less opposition, greatly increasing the risk of virus-driven lymphoma.
Precancerous Conditions on the Eye’s Surface
Conjunctival melanoma, which develops on the clear membrane covering the white of the eye, sometimes arises from a precursor condition called primary acquired melanosis (PAM). This appears as flat, pigmented patches on the conjunctiva. Not all PAM becomes cancerous. Cases with no or mild abnormal cell changes almost never transform into melanoma. But when PAM shows severe cellular abnormalities, 13 to 46 percent of cases progress to melanoma. Conjunctival melanoma can also develop from an existing mole (nevus) on the eye’s surface or appear without any preceding condition at all.
Cancer That Spreads to the Eye
Not all eye cancer originates in the eye. Metastatic tumors, cancers that started somewhere else and traveled to the eye through the bloodstream, are actually more common than primary eye tumors. The eye’s middle layer has an exceptionally rich blood supply, making it a natural landing site for circulating tumor cells.
Breast cancer is the most common source, responsible for 37 percent of uveal metastases. Lung cancer follows at 27 percent. After that, the numbers drop sharply: kidney cancer and gastrointestinal cancers each account for about 4 percent, with skin melanoma, prostate cancer, thyroid cancer, and others making up smaller shares. These metastatic tumors can cause vision changes, pain, or visible growths, and they sometimes lead to the discovery of a cancer the patient didn’t yet know about.
Risk Factors That Raise Your Odds
Several characteristics consistently appear in people who develop eye cancer:
- Light skin and eye color. People with fair skin, light-colored eyes, and an inability to tan easily have higher rates of uveal and conjunctival melanoma. Melanocytes in lighter eyes may be more vulnerable to DNA damage.
- Age. Uveal melanoma is most often diagnosed in people over 50. Retinoblastoma, by contrast, almost exclusively affects children under five.
- Family history. A family history of eye melanoma raises the likelihood of carrying a BAP1 mutation or other inherited predisposition.
- Existing eye conditions. An unusual mole (nevus) inside the eye or primary acquired melanosis on the conjunctiva can serve as a starting point for cancer.
- Weakened immune system. HIV infection, organ transplant medications, and other causes of immune suppression increase the risk of intraocular lymphoma.
- Occupational UV exposure. Long-term welding without proper eye protection is a recognized risk factor for ocular melanoma.
Many people diagnosed with eye cancer have no identifiable risk factor at all. The genetic mutations that initiate most uveal melanomas appear to arise spontaneously, without a clear external trigger. This makes routine eye exams especially valuable, since these cancers are often found incidentally during a dilated eye exam before any symptoms appear.