You may associate melanoma with skin cancer and the growth or spread of moles on the surface of your skin. However, melanoma doesn't occur just on your skin. It can also occur in your eyes and, rarely, in internal organs.

Melanoma develops in the cells that produce melanin — the pigment that gives your skin its color. Your eyes also have melanin-producing cells. Eye melanoma most commonly develops in the uvea, the vascular layer of your eye sandwiched between the retina and the white of the eye (sclera). Also called ocular melanoma, eye melanoma can occur in the front part of the uvea (iris and ciliary body) or in the back part of the uvea (choroid layer).

Melanoma that originates in your eye is termed a primary eye cancer. Eye melanoma is the most common type of primary eye cancer in adults, but it's rare. If the melanoma begins elsewhere and then spreads to your eye, it's called a secondary eye cancer; this also is rare.

Treatment is available for eye melanoma. The earlier it's detected, the better your chance for successful treatment. Getting regular eye exams can help detect eye melanoma at an earlier stage.

You may experience no symptoms at all for melanoma of the eye. On the other hand, eye melanomas may cause light flashes, blurring or a dark spot in your vision.

What to watch for

• A change in the color of the iris
• A growing dark spot on the iris
• A sensation of flashing lights
• Poor or blurry vision in one eye
• Loss of side (peripheral) vision in the affected eye
• Floaters (spots or squiggles drifting in your field of vision)
• A red and painful eye

Melanomas in the back portion of the eye usually are detected only during eye exams.

The exact cause of eye melanoma isn't known; however, it's not typically inherited. In recent years, scientists have developed a better understanding about the role that DNA plays in causing cells to become cancerous. DNA instructs the behavior of cells and therefore influences the risk of developing certain diseases, including some cancers.

Genetics can play a role
Some genes have the instructions for how cells should grow and divide. Defects (mutations) in DNA can cause these genes to malfunction, sometimes resulting in cancer. Sometimes these mutations are inherited, but usually they are acquired during life.

Definitive reasons about why these changes occur in some people, how the changes occur, and how the changes cause or promote the development of cancer are still not understood.

Risk factors for primary melanoma of the eye include:

• Eye color. Just as people with fair skin are more likely to develop melanoma of the skin, people with blue eyes are somewhat more likely to develop melanoma of the eye. Eye melanoma occurs less often in people with brown eyes.
• Genetic disposition. A rare condition called dysplastic nevus syndrome, which leads to abnormal moles of the skin and increased risk of skin melanoma, may increase your risk of developing melanoma of the eye. In addition, people with abnormal skin pigmentation involving the eyelids and adjacent tissues and increased pigmentation on their uvea — known as oculodermal melanocytosis or nevus of Ota — also have an increased risk of developing eye melanoma. Studies also have shown an association between certain abnormalities on chromosome 3 and increased risk that melanoma may spread from the eye to distant parts of the body.

Sun exposure
Although excessive exposure to sunlight has been proposed as a possible risk factor for melanoma of the eye, it has never been proved.

Some types of eye melanomas can be detected only by a doctor, so it's a good idea to have regular, routine eye examinations. Because this type of cancer is rare, there's no screening test other than an eye examination.

If you find a dark spot on your iris that is enlarging, have a doctor examine it. Many doctors believe that skin and eye melanomas start from a mole (nevus), which is a noncancerous tumor of pigment cells. If you have a nevus or a freckle in your eye, have it checked regularly by an eye doctor.

Having a regular examination of your eyes by a doctor specializing in diseases of the eye (ophthalmologist) is the first and most important step in early detection and diagnosis of eye melanoma.

Your doctor will examine the outside of your eye, looking for enlarged blood vessels that can indicate a tumor inside your eye. Then, with the help of instruments, your doctor will look inside your eye. One method, called ophthalmoscopy, uses lenses and a bright light mounted on your doctor's forehead — a bit like a miner's lamp. Another method, called slit-lamp biomicroscopy, uses a microscope that produces an intense beam or line of light to illuminate the interior of your eye.

In most cases, looking inside your eye alone will be enough to detect and diagnose any tumors or other abnormalities.

Further evaluation of suspected melanoma
If your doctor suspects you may have eye melanoma, you may undergo one of a number of imaging tests:

• Ultrasound. This painless procedure uses high-frequency sound waves from a hand-held, wand-like apparatus called a transducer, which can produce precise images of structures within your body. It's an important test for diagnosing and evaluating eye tumors. Eye melanomas often have a characteristic appearance on the ultrasound. Your doctor also uses ultrasound to measure the thickness of the tumor to help determine the most appropriate treatment. The initial ultrasound further provides a baseline measurement for comparison as you go through your treatment plan.

  In this test you sit in a chair in your doctor's office. The transducer is placed against either your eyelid or the front surface of your eye, in which case your eye is numbed with anesthetizing drops. A lubricant placed on the transducer may run down your cheek, but there's no discomfort or pain. The test takes about 15 minutes.

• Angiography. Angiography is a process that uses dyes to help your doctor better visualize parts of your body. In a procedure called fluorescein angiography, your doctor injects a yellow dye into a vein in your arm. The dye circulates in your eyes, highlighting the blood vessels in your retina and providing information about the characteristics of the tumor. A camera with special filters takes flash pictures every few seconds for several minutes, providing your doctor with useful images. Another procedure called indocyanine green angiography involves injecting a green dye. Again, using special filters, your doctor can obtain useful images that may help define the characteristics of a tumor.

Determining further spread of the cancer
Your doctor may also recommend additional diagnostic procedures to determine whether the cancer has spread (metastasized) to other parts of your body. Eye melanoma can spread through your bloodstream. The liver and lungs are the organs most often affected. Tests may include:

• Blood tests. Blood tests to measure the function of your liver are common at the time an eye melanoma is first discovered, as well as during follow-up visits. Abnormalities may indicate whether the melanoma has spread to your liver.
• Chest X-ray. Your doctor may use this procedure to determine whether your eye cancer has spread to your lungs. This is unlikely unless the cancer is in advanced stages.

• Computerized tomography (CT). Computerized tomography is an X-ray technique that produces images of your internal organs that are more detailed than are those produced by conventional X-ray exams. Conventional X-ray exams use a stationary X-ray machine to focus beams of radiation on a particular area of your body to produce two-dimensional images. CT scans use an X-ray-generating device that rotates around your body and a powerful computer to create cross-sectional images, like slices, of the inside of your body.

  Often, after the first set of X-rays is taken, a contrast dye is injected intravenously and a second set of pictures is taken. The dye helps better outline structures in your body.

  If you have an eye melanoma, the CT scan will concentrate on your liver and lungs because they are the most common locations to which an eye melanoma is likely to spread.

• Ultrasonography. Your doctor may have you undergo ultrasonography to generate images of your liver and help determine whether the cancer has spread to your liver.
• Magnetic resonance imaging. Magnetic resonance imaging (MRI) is a technique that uses a magnetic field and radio waves to create cross-sectional images of your head and body. Your doctor uses these detailed, clear images to identify and diagnose a wide range of conditions. MRI is a noninvasive way for your doctor to examine your body. The exam is painless and lasts between 30 and 90 minutes. In some cases, contrast agents are injected into your veins to enhance the appearance of certain tissues or blood vessels in the images. Doctors don't routinely use MRI to assess eye melanomas because they can obtain the information they need by other, less expensive, methods above.

Tissue sample
If your doctor isn't sure whether a tumor is a melanoma, he or she may obtain a tissue sample (biopsy). This is usually done by placing a small needle into your eye and removing a sample of tumor cells. These cells are then evaluated in the laboratory. However, doctors usually can make a confident diagnosis of eye melanoma using methods other than biopsy.

After eye melanoma is diagnosed, you and your doctor will review your treatment options. Factors to be considered are the location and size of the melanoma, as well as your overall physical health.

Melanomas of the eye are rare, so it's a good idea to find a doctor with experience in treating these cancers. In addition, a second opinion can provide more information and help you feel more confident about your treatment plan.

Sometimes, doctors suggest observing a small lesion rather than treating it right away. But your doctor will generally recommend treatment for a medium-sized or large-sized melanoma.

Treatment designed to destroy a melanoma often will cause some loss of vision, even though every effort is made to preserve vision. But because cancers of the eye can be fatal, in some cases you'll need treatment even if it means loss of vision or loss of your eye.

Surgery is the foundation for most cancer treatments. If an eye melanoma is of a certain size and in a favorable location, treatment can sometimes be accomplished with surgery alone. Treatment for other eye melanomas may be done with radiation alone, or radiation combined with a therapy such as infrared laser.

Surgery
Depending on the characteristics of the tumor, your doctor may choose from a variety of surgical procedures to remove the melanoma:

• Iridectomy. This procedure removes only a part of the iris. It's used for small iris melanomas that have not invaded other structures of your eye.
• Iridotrabeculectomy. This procedure removes parts of the iris and the supporting tissues around the cornea at the base of the iris for small iris melanomas that have invaded those tissues.
• Iridocyclectomy. This is another treatment for small melanomas of the iris and ciliary body. It involves removing part of the iris and the ciliary body.
• Choroidectomy. Part of the choroid is removed during this surgery, with or without removing part of the wall of the eye (sclerouvectomy). This complicated procedure may be followed by supplementary radiation.
• Enucleation. This surgery removes the entire eye. This procedure is used for large eye tumors when alternative treatments would destroy most of the eye anyway. It's also commonly used if the eye has developed pain because of the tumor. An implant is inserted into the position where the eye was previously located, and the muscles are attached to it to provide normal movement for an artificial eye (prosthesis). The prosthesis is inserted later, between the lids, after the tissues have healed. Movement of the implant transmits motion to the artificial eye.

Radiation therapy
Carefully targeted and regulated doses of high-energy radiation — radiation therapy — can destroy ocular melanoma and be lifesaving.

Radiation therapy damages cells by destroying the genetic material that controls how cells grow and divide. And although both healthy and cancerous cells are damaged by radiation, the goal of treatment is to hurt as few normal, healthy cells as possible.

Doctors generally reserve radiation treatment for eye melanomas to medium-sized and large-sized melanomas. The radiation dose can be delivered with charged particles such as proton beams, which are generated from outside of your body and directed into your eye ( teletherapy ). Or, the radiation can come from small radioactive seeds that are temporarily anchored to your eye ( brachytherapy ).

In brachytherapy, a small implant (plaque) similar to a bottle cap and containing several radioactive seeds (usually iodine-125 seeds) is sutured to the wall of your eye at a site overlying the tumor. The plaque remains in place for several days until it has delivered an optimal amount of radiation for the characteristics of your tumor. The device is then removed, and your doctor will monitor the tumor at regular intervals to watch for tumor shrinkage.

Small eye melanomas
There has been a recent trend toward treating small eye melanomas with either radiation therapy or transpupillary thermotherapy (TTT) — a type of infrared laser therapy — or both. Destroying the cancerous tissue by freezing it (cryotherapy) also has been used for some small eye melanomas.

A clear association between sunlight and melanomas of the skin has been established. This same association has not been established for melanomas of the eye.

Eye melanoma may result in partial or complete loss of vision and, in some cases, removal of the eye (enucleation). Although these outcomes are traumatic, you can overcome them with the support of friends and family, adequate time to heal and adjust, and modern technology.

If your cancer treatment leaves you with vision in only one eye (monocular vision), it's still possible to do practically everything you were able to do with two working eyes. But you'll need to make adjustments, primarily regarding your ability to judge distance, and it may be more difficult to be aware of things around you, especially things occurring on the side without vision.

If your eye must be removed, it will be replaced by a round implant and then covered by your own tissue. Your eye muscles will be attached to the implant so that the implant will move.

After several weeks, an artificial eye (prosthesis) is made. The front surface of your new eye will be custom-painted to match your existing eye, and the back surface will be custom-molded so it fits comfortably. Motion from the implant is transferred through the healed tissue to the prosthetic eye, in most cases providing a satisfactory cosmetic appearance.

You'll be able to sleep with this new eye, but you'll have to remove it occasionally for cleaning. In most cases, these artificial eyes last for decades.