Encyclopedia - Choroidal Melanoma

How is choroidal melanoma detected?
What treatments are used for choroidal melanoma?

Choroidal melanoma is a primary cancer of the eye and is the most common intraocular tumor in adults. It arises from the pigmented cells of the choroid, a tissue full of blood vessels that nourish the retina at the back of the eye. Appearing as a small freckle beneath the retina, choroidal melanoma can grow in height and diameter and may, if not treated, eventually spread to other parts of the body.

Some choroidal melanomas appear to remain dormant. However, most enlarge slowly over time and lead to loss of vision if not treated. All choroidal melanomas should be treated as if they are malignant.

How is choroidal melanoma detected?

Because it occurs inside the eye and is not visible to patients, persons with a choroidal melanoma may not recognize its presence until the tumor has grown so large that vision is impaired.

The tumor is usually diagnosed during an eye examination. It is visible through the "window" of the eye provided by the pupil, and the eye doctor will recognize the choroidal melanoma by the degree of pigmentation of the tumor, its shape, location, and other features. Ophthalmologists can make a diagnosis based on clinical appearance, photographs, and an ultrasound exam.

Ultrasound is a test that transmits high frequency sound waves into the eye. The sound waves are reflected by ocular tissues and used to create a picture of the internal structure, which is displayed on a screen. The A-scan ultrasound is accurate in estimating the height of the tumor, while the B-scan shows orbital shadowing, which is a dark area behind the tumor.

In fluorescein angiography, a fluorescent dye is injected into a vein in the arm. As the dye passes through the blood vessels in the back of the eye, rapid sequential photographs are taken through the pupil. The information provided by these tests describes the size of the tumor.

What treatments are used for choroidal melanoma?

Treatment of choroidal melanoma is recommended when doctors determine that the tumor is likely to grow and spread to other parts of the body if left untreated. Traditionally, treatment for choroidal melanoma has been enucleation, which is removal of the eye. As long as the tumor has not spread to other parts of the body, eye removal eliminates the tumor. However, work has been done in the past 20 years to develop alternative methods of therapy, particularly for those eyes with good vision.

Radiation therapy is the most frequently used alternative for treating choroidal melanomas. Treatments, at the appropriate dose rates and in the proper physical forms, are intended to eliminate tumor cell growth without damage to normal tissue. The radiation kills a tumor either by producing free radicals that destroy cellular DNA immediately or by inducing mutations that kill tumor cells over a period of time. As the cells die, the tumor shrinks, but it usually does not disappear entirely. Radiation can serve as an alternative to enucleation or as a preliminary treatment before eye removal in order to decrease the likelihood of metastasis.

Other methods of therapy are available for selected tumors. Laser photocoagulation can be used to ablate small thin tumors. Cryotherapy, or freezing, is sometimes used to kill very small tumors. Under certain circumstances, small tumors, especially those located near the front of the eye, can be surgically removed using an eye-sparing technique known as an eye wall resection.

No treatment of choroidal melanoma is available that can guarantee to destroy the tumor, to preserve vision, or to assure a normal life span.