Eye melanoma, also called ocular melanoma, is a rare type of eye cancer that arises in melanocytes. These pigmented cells occur in several different tissues in the eye. An eye melanoma can develop from an obvious benign mole in the eye or from tissue that does not appear obviously pigmented.

Anyone can get eye melanoma but fair-haired and fair-skinned people seem to be at a higher risk, particularly if they have ocular melanocytosis or dysplastic nevus syndrome. [Link to condition page on dysplastic nevus syndrome when completed] Those affected have large numbers of irregular or abnormal moles in the skin, usually more than a hundred.

Types of eye melanoma
Ocular melanoma is not a common cancer. It can be classified according to the site in the eye where it develops:

  • Conjunctival melanomas arise in the conjunctiva, the connective tissue at the front of the eye, just under the eyelids.
  • Uveal melanomas start in the uveal tract inside the eye. This group of tissues includes the iris, the ciliary body and the choroid.
  • Uveal melanomas include 3 subtypes:
  • Iris melanomas are usually very small and may occur on the iris or just behind it.
  • Ciliary body melanomas occur in the part of the eye that controls lens movements. The symptoms often only become evident at a later stage due to their location.
  • Choroidal melanomas arise in the choroid, the layer of blood vessels that lies behind the retina and in front of the sclera (the white of the eye).

Symptoms of eye melanoma
Conjunctival melanomas often cause a dark spot on the surface of the eye. This type of discoloration can be due to other causes, such as a benign mole, so the dark spot does not always mean eye cancer. Only a few people with eye melanoma experience symptoms. In some cases of uveal melanoma, the vision can become blurred, and the person affected might see flashes of light and shadows.

Many eye melanomas cause no symptoms at all and are often found at routine optician visits. This is particularly true if the eye melanoma is a transformation from a benign mole into a malignant melanoma. It is therefore well worth having regular eyesight checks. Even if you can see perfectly, regular screening by an optician can detect an eye melanoma early so that you can get prompt treatment.

An eye melanoma is usually easily visible to a trained optician or ophthalmologist but a definite diagnosis requires an expert review with an ocular oncologist.

Diagnosis of eye melanoma
An ocular oncologist will look for features that can distinguish an eye melanoma from other forms of eye cancer. For example, eye melanomas in the choroid, the rich layer of blood vessels under the retina, can produce lipofuscin. This orange pigment is present on the surface of the tumour, particularly those that develop under the retina, and can be detected easily.

Eye ultrasound and photography are usually used to diagnose eye melanomas that occur in the uveal tract.  Ultrasound techniques can also be used to work out the size of an eye melanoma fairly accurately. Its position within the eye can also be mapped, which is useful for accurate placement of radiotherapy. Tumours at the front of the eye can be biopsied or removed.