How is melanoma of the eye diagnosed?
Certain signs and symptoms might suggest that a person could have eye cancer, but tests are needed to confirm the diagnosis.
Signs and symptoms of eye melanoma
Many patients with eye melanoma don’t have symptoms unless the cancer grows in certain parts of the eye or becomes more advanced. Signs and symptoms of eye melanomas can include:
- Problems with vision (blurry vision or sudden loss of vision)
- Floaters (spots or squiggles drifting in the field of vision) or flashes of light
- Visual field loss (losing part of your field of sight)
- A growing dark spot on the iris
- Change in the size or shape of the pupil
- Change in position of the eyeball within its socket
- Bulging of the eye
- Change in the way the eye moves within the socket
Pain is rare unless the tumor has grown extensively outside the eye. In such cases, bulging or a change in the position of the eye may also be noted.
Other, less serious conditions can also cause many of these symptoms. For example, floaters may occur as a normal part of the aging process. Still, if you have any of these symptoms, it’s important to see a doctor right away so the cause can be found and treated, if needed.
Examination of the eye by an ophthalmologist (a medical doctor specializing in eye diseases) is often the most important step in diagnosing melanoma of the eye. The doctor will ask if you are having any symptoms and check your vision and eye movement. The doctor will also look for enlarged blood vessels on the outside of the eye, which can be a sign of a tumor inside the eye.
The ophthalmologist may also use special instruments to get a good look inside the eye for a tumor or other abnormality. You may get drops in your eye to dilate the pupil before the doctor uses these instruments.
- An ophthalmoscope (also known as a direct ophthalmoscope) is a hand-held instrument consisting of a light and a small magnifying lens.
- An indirect ophthalmoscope and a slit lamp is more like a large microscope. For this exam, you sit down and rest your chin on a small platform, while the doctor looks into your eye through magnified lenses. This exam can often give a more detailed view of the inside of the eye than the direct ophthalmoscope.
- A gonioscopy lens is a specially mirrored lens that is placed on the cornea (after it is numbed). This lets the doctor see the deep structures in the angle of the front of the eye near the iris. It can be used to look for tumor growth into areas of the eye that would otherwise be hard to see.
Most of the time if a person has melanoma of the eye, the doctor can make the diagnosis with an eye exam alone. In some cases, imaging tests such as ultrasound may be needed to confirm the diagnosis. Very rarely a biopsy will also be needed.
Some people might have a benign tumor in the eye called a choroidal nevus, which can sometimes be mistaken for an eye melanoma. A small number of these will eventually turn into melanomas. If your ophthalmologist spots one of these, he or she will likely advise regular eye exams to see if it grows.
Even if you recently had an eye exam, if you start to have any of the symptoms listed above, get another exam. Sometimes these tumors are missed or grow so fast that they weren’t there when you were last examined.
If an eye exam suggests you might have eye cancer, more tests will likely be needed. These might include imaging tests or other procedures.
Imaging tests use sound waves, x-rays, or magnets to create pictures of the inside of your body. Imaging tests may be done for a number of reasons, including to help find a suspicious area that might be cancerous, to learn how far cancer might have spread, or to help determine if treatment has been effective.
Ultrasound (echography): This is a very common test for helping to diagnose eye melanomas. Ultrasound uses high-frequency sound waves to make pictures of parts of the body. For this test, a small wand-like instrument is placed up against the eyelid or eyeball, and high frequency sound waves are sent through the eye. The instrument picks up the pattern of echoes that comes back, which is converted into an image on a computer screen.
This test is especially useful for diagnosing eye melanomas because they look a certain way on ultrasound. Using this test, doctors can confirm a diagnosis of melanoma of the eye in most cases. This test can also show the location and the size of the tumor.
Ultrasound biomicroscopy (UBM) is a special type of ultrasound that uses sound waves at even higher frequency to image the front parts of the eye.
Optical coherence tomography (OCT) is a similar type of test that uses light waves instead of sound waves to create very detailed images of the back of the eye.
If you have already been diagnosed with eye melanoma, an ultrasound of the abdomen may be done to look for tumors in the liver, which is a common site of spread of this cancer.
Fluorescein angiography: For this test, an orange fluorescent dye (fluorescein) is injected into the bloodstream through a vein in the arm. Pictures of the back of the eye are then taken using a special light that causes the dye to fluoresce (glow). This lets the doctor 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 tell if something is not a melanoma.
When a special green dye is used to look at the blood vessels, this test is known as indocyanine green (ICG) angiography.
Chest x-ray: If you have been diagnosed with eye melanoma, a plain x-ray of your chest may be done to see if the cancer has spread to your lungs. This is very unlikely unless your cancer is far advanced. This x-ray can be done in any outpatient setting. If the results are normal, you probably don’t have cancer in your lungs.
Computed tomography (CT or CAT) scan: A CT scan is sometimes used to see if a melanoma has spread outside of the eye into nearby structures. It may also be used to look for spread of the cancer to distant organs such as the liver.
The CT scan uses x-rays to produce detailed cross-sectional images of parts of the body. Instead of taking one picture, like a standard x-ray, a CT scanner takes many pictures as it rotates around you. A computer then combines these pictures into detailed images of the part of your body being studied. Before the scan, you may be asked to drink a contrast solution and/or get an intravenous (IV) injection of a contrast dye that helps better outline structures in the body. You may need an IV line through which the contrast dye is injected. The injection can cause some flushing (redness and warm feeling). Some people are allergic and get hives or, rarely, more serious reactions like trouble breathing and low blood pressure. Be sure to tell the doctor if you have any allergies or have ever had a reaction to any contrast material used for x-rays.
A CT scanner has been described as a large donut, with a narrow table that slides in and out of the middle opening. You need to lie still on the table while the scan is being done. CT scans take longer that regular x-rays, and you might feel a bit confined by the ring you have to lie in while the pictures are being taken.
Magnetic resonance imaging (MRI) scan: MRI scans are often used to determine the extent of a tumor’s growth and spread. They are particularly useful in looking at eye tumors. They are also helpful in finding cancer that has spread to the brain or spinal cord, as well as any spread of melanoma outside the eye orbit.
Like CT scans, MRI scans provide detailed images of soft tissues in the body. But MRI scans use radio waves and strong magnets instead of x-rays. The energy from the radio waves is absorbed and then released in a pattern formed by the type of body tissue and by certain diseases. A computer translates the pattern into very detailed images of parts of the body. A contrast material called gadolinium is often injected into a vein before the scan to better see details. MRI scans take longer than CT scans — often up to an hour – and are a little more uncomfortable. You lie on a table that slides inside a narrow tube, which can feel confining and may upset people with a fear of enclosed spaces. Newer, open MRI machines might help with this, but they might provide less detailed images and can’t be used in all cases. The machine also makes buzzing and clicking noises that may be disturbing. Some people might need medicine to help them relax for the test.
For more information on imaging tests, see our document Imaging (Radiology) Tests.
For most types of cancer, the diagnosis is made by removing a small piece of the tumor and looking at it under a microscope for cancer cells. This is known as a biopsy.
A biopsy is not often needed for eye melanomas because almost all cases can be accurately diagnosed by the eye exam and imaging tests. Many doctors prefer not to do biopsies because it is hard to get a sample of the tumor without damaging the eye. Also, there’s a chance the biopsy could possibly spread the tumor within or outside of the eye.
A biopsy can be done either with sedation and local anesthesia (numbing medicine) or while a person is under general anesthesia (in a deep sleep). A thin, hollow needle is passed into the eye, and cells from the tumor are sucked up into a small syringe. The sample is sent to a lab, where a doctor called a pathologist looks at the cells under a microscope.
While most people with melanoma of the eye are treated without having a biopsy first, this may change in the future. New technology may make biopsy safer in situations where the diagnosis is uncertain. In recent years, some doctors have started using biopsies to get a sample of the tumor for testing. This testing can help tell whether the melanoma is likely to come back outside of the eye at some point. (See “What’s new in eye cancer research and treatment?” for more information.)
Blood tests can’t be used to diagnose melanoma of the eye, but they may be done once a diagnosis is made.
Liver function tests: If you have been diagnosed with eye melanoma, your doctor may order blood tests to see how well your liver is working. Abnormal test results can sometimes be a sign that the cancer has spread to the liver.
Last Medical Review: 09/13/2013
Last Revised: 09/13/2013