Eye cancer is very rare, but occurs most often in Caucasian people over 60 years old who have light-coloured hair and eyes, as well as pale skin. The most common type of cancer of the eye is malignant melanoma, which usually occurs in the uvea, or middle layer of the eye. The uvea includes the iris and the ciliary body. About five percent of all melanomas occur in the eye.
Risk factors associated with this disease are:
- Primary acquired melanosis – a rare condition present at birth that consists of a clear mucous membrane that covers the inner surface of the eyelids and the outer surface of the eye and appears as a brown flat patch.
- Ocular melanocytosis – abnormal proliferation of melanocytes in and around the eyes.
- Light-coloured skin, eyes, and hair.
- Moles on the skin.
- Indoor tanning.
- Welding and exposure to UV light (ex. sunlight) without proper ocular protection.
- HIV or AIDS – this lowers the body’s immunity and can give rise to precursors of eye cancer.
Symptoms of eye melanoma are not usually present; however, when present, they can manifest as blurred vision, seeing flashing lights and shadows, and/or brown or dark patches on the white area of the eye. An opthalmologist can diagnose and differentiate malignant and benign conditions of the eye.
In order to arrive at a diagnosis, the physician will examine the eye up close with an ophthalmoscope or bimicroscope to identify a lesion and take a biopsy. This small tissue sample will be analyzed in the laboratory to determine the type of cancer. Other tests for eye melanoma can include:
- Transillumination, to pinpoint exactly where the tumour is located.
- Colour fundus photography is a picture of the back of the eye taken before and after treatment.
- Positron emission tomography (PET)/CT scan, to obtain a detailed picture of the eye and surrounding region.
- MRI forms a detailed picture of the structure of the eye and surrounding tissues.
Staging and grading will determine the course of treatment and the prognosis for each individual patient. An early or localized stage means that the cancer is located in the eye and has not spread. Advanced stage describes a tumour that has spread beyond the eye to the adjacent tissues, or even to other organs such as the lungs or liver. High-grade denotes an aggressive tumour, while low-grade tends to grow slowly.
Depending on the staging and grade of the tumour, different courses of treatment will be favoured:
- Radiotherapy may be the only treatment necessary in cases of uveal melanoma.
- Surgery can involve a small resection of the tumour or a partial or complete removal of the eye depending on the size and location of the tumour.
- Transpupillary thermotherapy (TTT) is performed using a laser to destroy any remaining malignant cells after treatment of small melanomas.
- Cryotherapy uses cold to freeze the area where the tumour is located and is usually used after surgery.
- Chemotherapy eye drops.
- Photodynamic therapy (PDT) uses a light sensitizing agent to target and kill cancer cells.