What is Ocular Melanoma
Melanoma is a type of cancer that develops from melanocytes, the cells that give color to the skin and eyes. Melanoma usually arises on the skin and mucous membranes but can also occur in the eyes.
Some eye tumors form on the surface of the eye and eyelid, very similar to skin melanomas. However, ocular melanoma can also develop on the inner part of the eye. The tumor cells grow in the uvea – a layer of tissue beneath the white part of the eye – which contains melanocytes. Therefore, uveal melanoma is another name for ocular melanoma.
It is the most common form of eye cancer in adults, although it is a rare disease. It can cause vision problems and be serious if it spreads to other organs.
Types of Ocular Melanoma
The uvea contains three parts, and melanoma can arise in any of them. The classification for ocular melanomas is based on the location of the cancer, and its subtypes are:
- Melanoma of the iris – formed in the colored part at the front of the eye (iris);
- Melanoma of the ciliary body – occurs in the part that releases fluid to the eye and changes the shape of the lens to help focus. When cancer is in the ciliary body, it can push the eye’s lens out of place and blur vision;
- Choroidal melanoma – the part that contains blood vessels to nourish the eyes. It is most likely that cancer starts and grows in the choroid, followed by the ciliary body and then the iris. Some people have cancer in more than one of these three areas at the same time; and
- Conjunctival melanomas – the conjunctiva is a thin, transparent covering over the sclera (hard, white layer that covers most of the outer area of the eyeball). These melanomas are extremely rare. Since they can spread through the blood and lymphatic system, they can also reach distant organs such as the lungs, liver, or brain.
Symptoms and signs of ocular melanoma
Many patients with ocular melanoma are asymptomatic, meaning they do not show any symptoms of the disease. When symptoms do occur, it is because the disease is already advanced or has grown in certain parts of the eye.
Among the symptoms of ocular melanomas, the most frequent are:
- Blurry vision or vision loss;
- Floaters (spots or squiggles floating in the field of vision) or flashes of light;
- Loss of visual field;
- Growing dark spot on 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 how the eye moves within the socket.
Diagnosis of ocular melanoma
The fact that the symptoms are similar to those caused by other conditions can delay diagnosis. In most cases, doctors notice an ocular melanoma during a routine eye exam because the tumors are darker than the surrounding area or produce fluid. If this occurs, tests will be requested to confirm the diagnosis. 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 captures the echoes as they bounce back from organs. The echoes are converted into an image on a computer screen. Using this test, doctors can confirm the diagnosis of eye melanoma 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) – 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 cancer spread to distant organs, such as the liver;
- Fluorescein angiography – the patient is given a special dye injected into a vein that through the bloodstream reaches the eye. Photos 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 have a special appearance with this test, some other eye problems do. Doctors can use this method to know if something is not a melanoma;
- Magnetic resonance imaging – particularly useful for observing eye tumors and their spread outside the eye socket, to places like the liver. MRIs provide detailed images of the body’s soft tissues using radio waves and strong magnets instead of x-rays; and
- Photographic imaging – it is also possible for the ophthalmologist to take a photo of a nevus (mole or spot on the eye) at each visit to track changes in these areas. Larger, thicker nevi are more likely to turn into cancer.
Almost all cases can be accurately diagnosed through ophthalmologic examination and imaging tests. In rare cases, when such tests do not provide a definitive answer, the doctor may take a tissue sample from the eye to examine it under a microscope, performing a biopsy.
Sometimes, the biopsy can be useful to check for certain genetic mutations that may predict outcomes (prognosis), as well as help choose targeted cancer drugs. Additionally, certain ocular melanomas can spread for many years before being diagnosed—thus, early biopsy of a concerning area may be helpful. If a biopsy is needed, it can be done with sedation and local anesthesia or under general anesthesia.
Treatment for ocular melanoma
The main factors determining the treatment for intraocular melanoma include the size relative to local structures, the staging of the disease in relation to distant structures, and the possibility of preserving vision.
Choroidal melanoma
The treatment for this type of tumor depends on its size and the function of the affected eye region. The smaller the tumor, the less likely surgery is needed, unless the eye is damaged due to the tumor or vision has already been lost.
There are several options for treating choroidal melanomas: watchful waiting, radiotherapy, laser therapy, and surgery. An experienced ophthalmologist analyzes each case individually to determine the appropriate protocol. Radiotherapy and surgery appear to be equally effective. Radiotherapy offers the chance to preserve vision, but some patients who undergo radiotherapy may also need surgery.
Iris melanoma
They are usually small tumors that grow slowly. A series of special images will be taken 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 iris melanomas include:
- Iridectomy – removal of part of the iris;
- Iridotrabeculectomy – removal of part of the iris, as well as a small portion of the outer part of the eyeball;
- Iridocyclectomy – removal of a portion of the iris and ciliary body; and
- Enucleation – removal of the eyeball.
Melanoma of the ciliary body
These rare tumors can be treated surgically if they are small, or with radiotherapy. In more advanced cases or if there are severe eye lesions, enucleation may be necessary.
Conjunctival melanoma
They are more prone to develop in local structures and spread to other organs, such as the liver and lungs. Treatment focuses on surgical removal of the tumor.
Advanced and recurrent melanomas
Most uveal melanomas are contained within the eye at the time of initial diagnosis. However, 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 enucleation surgery (removal of the eyeball).
When recurrence is extraocular, it most commonly occurs in the liver, but 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 tumors or block blood supply, in addition to immunotherapy.
Prevention of ocular melanoma
Ocular melanoma is a rare cancer, and there are no widely recommended screening tests for this type of tumor in people at low or medium risk. However, some eye cancers can be detected early.
Regular eye exams are an important part of everyone’s healthcare, even if they don’t have symptoms. Often, ocular melanomas are found during a routine eye exam. When the doctor looks through the pupil at the back of the eye, they may see a dark spot that suggests the possibility of an early melanoma.
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