Ocular melanoma is a cancer of the melanocytes, the cells that give our eyes their color. Despite occurring infrequently, it is the most common type of eye cancer in adults. Regular ophthalmological visits are crucial for early diagnosis. Find out more.
A melanoma is a type of cancer that affects the melanocytes, the cells that give our eyes their color. Although rare, this is the most common type of cancer in adults.
A melanoma is a type of cancer that affects the melanocytes, the cells that give our skin and eyes their color. Melanomas generally affect the skin and mucous tissues, but they can develop in the eyes as well. Some ocular cancers occur on the surface of the eye and on the eyelid, in a similar way to those affecting skin and mucous tissues. However, ocular melanoma can also develop inside the eye. Tumoral cells grow within the UVEA – the layer of tissue above the white part of the eye -, which contains melanocytes. Because of this ocular melanoma is also known as uveal melanoma.
This is the most common type of eye cancer occurring in adults, despite its rarity. It can cause issues with eyesight, and in the most serious cases it can spread to other organs.
Types of ocular melanoma
The uvea is divided in three parts, and melanoma can occur in any of them. Classification of ocular cancers is based on the place from which they develop, such as:
- Iris melanoma: occurring in the coloured area at the front of the eye (iris);
- Ciliary body melanoma: appears on the area that releases fluid into the eye and changes lens shape to help focusing. When the tumor is on the ciliary body, it may push and dislodge the eye lens, blurring the patient’s vision
- Choroid melanoma: occurring in the area where the blood vessels that irrigate the eye are. Choroid melanoma is the most frequent uveal cancer, followed by ciliary body melanoma, and iris melanoma. Some people can be affected by the cancer in all three areas at the same time; and
- Conjunctival melanomas: conjunctiva is the thin, clear membrane that covers the sclera (the hard, white layers that covers most of the external part of the eye).This melanoma is extremely rare, but as they can spread to the lymphatic and the circulatory systems, it can reach eve distant organs such as the liver, the lungs or the brain.
Symptoms and signs of ocular melanoma
Many ocular melanoma patients are asymptomatic, which means they don’t show any sign of being ill. When symptoms do occur it is because the cancer is already advanced, or it is growing in specific areas of the eye.
Among the symptoms of ocular melanoma, the most frequent include:
- Blurred vision or vision loss;
- Floaters (spots or squiggles floating in the field of vision) or flashes of light;
- Visual field loss;
- Increasing dark spotting in the colored part of the eye (iris);
- Change in the size or shape of the pupil;
- Change in the position of the eyeball within its socket;
- Protruding eye; and
- Change in the way the eye moves within its socket.
- Diagnosis of ocular melanoma
Diagnosis can be delayed by the fact these symptoms can point to several other conditions. In the majority of cases, doctors notice ocular melanomas during routine ophthalmological check-ups, because the tumors appear darker than the area surrounding them, or because they leak fluid. If this happens, the doctor will order further exams to confirm the diagnosis.
The imaging tests used in the diagnosis of ocular melanoma are:
- Ultrasound – is a very common test to help diagnose ocular melanomas. A small wand-like instrument is placed against the eyelid or eyeball, sends sound waves through the eye and picks up the echoes as they bounce off the organs. The echoes are converted into an image on a computer screen. Using this test, doctors can confirm the diagnosis of melanoma of the eye in most cases;
- Optical coherence tomography (OCT) – similar to an ultrasound, this test uses light waves instead of sound waves to create very detailed images of the back of the eye;
- Computed tomography (CT) scan – this is a scan sometimes used to check if a melanoma has spread outside the eye to nearby structures. It can also be used to detect the spread of cancer to distant organs, such as the liver;
- Fluorescein angiography – the patient receives a special dye injected into a vein that through the bloodstream reaches the eye. Pictures of the eye are taken using a special light that makes the dye fluorescent (bright). This allows the doctor to see the blood vessels inside the eye. Although melanomas do not look special with this test, some other eye problems do. Doctors can use this method to tell if something is not a melanoma;
- MRI imaging – particularly useful for looking at eye tumors and their spread outside the eye socket, in places such as the liver. MRI scans provide detailed images of the body’s soft tissues, using radio waves and strong magnets rather than x-rays; and
- Photo imaging – it is also possible for the ophthalmologist to take a photo of a nevus (mole or speck in the eye) at each visit to track changes in these areas. Larger, thicker nevus are more likely to develop into cancer.
Almost all cases can be accurately diagnosed by eye examination and imaging tests. In rare cases, when such tests do not provide a definitive answer, the doctor may take a fragment of eye tissue to examine it under a microscope, performing a biopsy.
Sometimes, a biopsy can be useful to check for certain genetic mutations that can predict outcomes (prognosis), as well as help choose targeted cancer drugs. Also, certain ocular melanomas can spread for many years before they are diagnosed – so having an early biopsy of an area of concern can be helpful. If a biopsy is necessary, it can be done with sedation and local anesthesia or under general anesthesia.
Ocular melanoma treatment
The main factors in determining the treatment for intraocular melanoma include the size in relation to local structures and the staging of the disease in relation to distant structures, as well as the possibility of preserving vision.
Choroidal melanoma
Treating this type of tumor depends on its size and the function of the affected region of the eye. The smaller the tumor, the less likely surgery is, unless the eye is damaged by the tumor or vision has already been lost.
There are several options for the treatment of choroidal melanomas: expectant waiting, radiation therapy, laser therapy, and surgery. The experienced ophthalmologist analyzes each case individually to define which protocol to adopt.
Radiotherapy and surgery seem to be equally effective. Radiation therapy offers the chance to preserve vision, but some patients who undergo radiation therapy may also need surgery.
Iris melanoma
These are usually small, slow growing tumors. A special imaging series will be performed to monitor the tumor, and treatment may consist of surgery or radiation therapy. If surgery is indicated, the amount of eye tissue to be removed will depend on the extent of the tumor. Types of surgery for early melanomas of the iris include:
- Iridectomy – removal of part of the iris;
- Iridotrabeculectomy – removal of part of the iris, plus a small portion of the outer part of the eyeball
- Iridocholectomy – removal of a portion of the iris and the ciliary body; and
- Enucleation – removal of the eyeball.
- Ciliary Body Melanoma
These rare tumors can be treated surgically, if they are small, or with radiation therapy. In more advanced cases or if there is severe eye damage, enucleation may be necessary.
Conjunctival melanoma
They are more likely to develop in local structures and to spread to other organs, such as the liver and lungs. Treatment is focused on surgical removal of the tumor and adjuvant treatment.
Advanced melanomas and relapses
Most uveal melanomas are contained in the eye at the time of initial diagnosis. But unfortunately, in about half of patients, the melanoma will recur at some point after treatment. Tumors that recur within the eye (intraocular recurrence) are usually treated with eyeball enucleation surgery (removal of the eyeball).
When the recurrence is extraocular, it is most often in the liver, but it can also occur in other areas, such as the lungs or bones. Treatment may include surgery, radiation therapy, heat or freeze ablation, or injection of drugs or other substances into the liver to destroy the tumors or block the blood supply.
Ocular melanoma prevention
Ocular melanoma is a rare type of cancer, and there are no widely recommended diagnostic tests for people at low or medium-risk, but some types of ocular cancer can still be detected in the early stages.
Regular ophthalmological check-ups are an important part of healthcare for everybody, even in the absence of symptoms. Ocular melanomas are very frequently spotted during these routine check-ups. When the doctor looks at the back of the eye through the pupil they can see the dark spot that suggests the presence of an early-stage melanoma.
