Eye cancer risks and causes

There are many different kinds of eye tumour and we know more about the risks for some than others. Eye cancer is rare in the UK, with around 430 cases diagnosed each year. Compared to around 40,000 cases of bowel cancer each year, you can see how rare eye cancer is. 

It affects roughly the same numbers of men and women. But some types of eye tumour, such as melanoma and squamous cell cancer, are slightly more common in men. Melanoma of the eye is much more common in white than black people. We aren't yet sure why this is. Some researchers think it may be because lighter eyes are more sensitive to sunlight.

Anything that increases your risk of getting a disease is a risk factor. Different cancers have different risk factors. Having one or more risk factors of a disease does not mean that you will definitely get it.

We know of a few possible risk factors for eye cancer. But researchers are investigating some factors that may turn out not to be risk factors.

We have included information about factors where there is enough evidence to say there is increased risk as well as factors that might affect risk.

The possible risk factors for eye melanoma include

• Eye colour
• Moles
• Too much sun exposure
• Exposure to UV radiation for some workers

Eye colour

People with blue, grey or green eyes are more likely to develop eye melanoma than people with brown eyes. In the same way, fair skinned people are more likely to get melanoma of the skin than people with darker skin.

People who have abnormal brown spots (pigmentation) on their uvea (called oculodermal melanocytosis) are at an increased risk of developing eye melanoma too.

Moles

Some families tend to have large numbers of moles on their skin, or moles that are unusual (doctors call them atypical). The atypical moles tend to be an irregular shape or colour. They also have a tendency to become cancerous. People with moles like this have a higher than average risk of skin melanoma and eye melanoma.

Sunlight

We know that over exposure to sunlight is a definite risk factor for melanoma of the skin. It has also possibly been linked to melanoma of the eye. Men who have higher exposure to sunlight through their work have an increased risk of eye melanoma. Exposure before the age of 30 seems to be most important. Natural ageing changes in the eye mean it is unlikely that exposure to sunlight in middle age causes eye melanoma.

Exposure to UV radiation for some workers

At least two studies have reported a slightly increased risk of melanoma of the eye in people working as welders. We don’t know whether it is UV radiation from the tools used for welding or other factors that cause the increased risk.

The risk factors for squamous cell eye cancer include

• Infection with HIV
• Drugs that suppress the immune system
• Human papilloma virus infection
• Sunlight

Infection with HIV

People who have HIV are at a higher risk of squamous cell carcinoma of the eye. This is almost certainly because of the effect of the virus on their immune systems.

Drugs that suppress the immune system

People who have an organ transplant need to take drugs to stop their immune systems rejecting the new organ. These drugs damp down the immune system generally. Because of this, these people are at an increased risk of some types of cancer, including squamous cell carcinoma of the eye.

Human papilloma virus infection

Human papilloma virus (HPV) may cause squamous cell carcinoma of the eye in combination with other factors. The virus causes squamous cell cancers elsewhere in the body. Researchers have found DNA from HPV in squamous cell cancers of the eye and in abnormal precancerous cells. People with squamous cell cancer of the eye have higher levels of antibodies to HPV in their blood than people without this type of cancer. Infection with HPV is very common and not everyone infected will get cancer. So there are probably other factors working with the HPV that explain why some people get it and others don’t. One of these co factors may be sunlight.

Sunlight

Sun exposure has been linked to a higher risk of squamous cell cancer of the eye. This type of cancer is more common in areas of the world where the sun’s light is stronger than in the UK.

Anyone whose immune system is not working as well as it should be may be more likely to develop a lymphoma of the eye. This includes people who

• Are taking drugs to stop organ rejection after a transplant
• Have AIDS
• Have autoimmune diseases such as rheumatoid arthritis
• Are born with rare medical syndromes which affect their immunity

Even so, people without any of these risk factors can still develop an eye lymphoma. As with other types of lymphomas, the risk appears to be increasing in people who don’t have problems with their immune systems, but we don’t know why this should be. The risk is highest between the ages of 40 and 60.

A bacteria called chlamydophila psittaci may increase the risk of a type of eye lymphoma called ocular adnexal malt lymphoma. Chlamydophila psittaci is caught by exposure to infected birds or domestic animals such as cats. It usually causes lung infections but can cause long term inflammation of the eye (conjunctivitis). Italian studies have linked ocular adnexal malt lymphoma to long term conjunctivitis due to chlamydophila psittaci. But studies in the United States have not shown an increased risk. So we need more research to see whether there is a link.

Kaposi's sarcoma of the eye is also called ocular Kaposi's sarcoma. People who have HIV or AIDS have a much higher risk of developing ocular Kaposi's sarcoma than the general population. But the risk is still small because ocular Kaposi's sarcoma is a very rare tumour.

Some eye cancers only affect children. Retinoblastoma is almost always diagnosed in young children. About 4 out of 10 retinoblastomas (40%) are due to an inherited faulty gene. This means they run in families.

Scientists are looking into the possible causes of retinoblastoma in people who haven’t inherited the faulty gene. One Swedish study has shown that children born to older mothers have a slightly higher risk of retinoblastoma. But, a more recent study did not find an increased risk for children of older mothers. One study has shown that children whose mothers smoked during pregnancy had double the risk of retinoblastoma but more studies are needed to confirm this.