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A malignant growth that grows in the eye is known as eye cancer. The term primary tumour is used to distinguish between cancers that develop within the eye and those that have spread from other cancers.
The eye consists of several layers and is divided into an anterior and posterior segment. The anterior segment comprises one-sixth of the total eye and is made up of the cornea, iris and lens. The cornea is transparent, curved and is linked to the larger posterior segment, composed of the vitreous, retina, choroid and the outer white shell called the sclera. The posterior chamber constitutes the remaining five-sixths; its diameter is typically about 24 mm. The cornea and sclera are connected by an area termed the limbus. The iris is the pigmented circular structure concentrically surrounding the centre of the eye, the pupil, which appears to be black. The size of the pupil, which controls the amount of light entering the eye, is adjusted by the iris’ dilator and sphincter muscles.
There are three types of eye cancer:
Eye melanoma is a rare type of cancer that is slow growing and does not present symptoms until later stages. In Belgium, around 80 patients are diagnosed with this type of cancer every year. The disease occurs more in men than in women, and most patients are between 50 and 80 years old at the time of diagnosis. Eye melanoma is usually detected at an early stage, and therefore the outlook is quite good, with a 5-year survival rate of 80%.
Due to the fact that eye melanomas grow slowly, it can take years before patients notice something is wrong. Early symptoms usually come from the melanoma growing into the retina. This can cause a number of symptoms, among which:
Little is known about what causes eye melanoma, though the illness does seem to occur in families that have a history of melanoma. There may be a correlation with a defect in the BAP1 gene, which is associated with a greater risk of developing a tumour. Recently, research has shown that people with light coloured irises are more prone to eye melanoma than people with dark irises.
A GP who suspects eye melanoma in a patient will refer their patient to an eye specialist who will conduct specialised examinations. They, in turn, may refer the patient to a specialised hospital for further testing. These tests include:
Other means of examination include biopsy and tests to determine whether the cancer has spread, such as X-rays, ultrasounds, CT scans and MRI scans.
As in most cancers, the stage of eye cancer is determined using the TNM system, although most specialists prefer to use the COMS rating system, meaning Collaborative Ocular Melanoma Study. This system distinguishes between small, medium-sized and large tumours.
When the diagnosis has been established and the stage of the tumour has been determined, specialists will come up with a treatment strategy. In case of eye melanoma, the options are surgery or radiation therapy. These treatments both bear the risk of causing damage to the eye, which can lead to partial or even complete loss of vision.
Three types of radiation therapy are possible:
In half of eye cancer patients, the tumour does spread, and when it does, it usually means that healing is no longer the target for the treatment. Instead, the focus shifts to palliative care, which is all about lengthening the life span and minimising discomfort. In an advanced setting, targeted therapy with PD-L1 and BRAF inhibitors may be an option for eligible patients. Targeted therapy continues to be an active area of research.
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