Melanoma is defined as a type of cancer that develops in cells that produce melanin called melanocytes. It can develop in the eye in which case it is alternatively known as eye melanoma, melanoma of the eye, uveal melanoma, intraocular melanoma, ocular melanoma, and OM.
Definition & Facts
Melanin is the pigment that gives skin its color. The eye contains melanocytes or melanin-producing cells, and melanomas can develop within those cells in the eye. Since most eye melanomas develop in areas of the eye not readily visible, they can be difficult to detect.
Ocular melanoma is the most common cancer of the eye for adults. According to the Ocular Melanoma Foundation, approximately 2,000 to 2,500 Americans are diagnosed every year with this disease. There are three areas of the eye where eye melanomas typically develop; they are known as the uvea or middle layer of the eye and include the following components: iris, ciliary body, and choroid.
Symptoms & Complaints
Symptoms include commonly reported perceptual changes in the eye such as blurred vision and a sensation of flashing lights. In some cases, loss of vision in the affected eye may occur. Physical changes include a dark spot on the iris and a change in the shape and/or size of the pupil.
The causes of ocular melanoma are unknown. As with any cancer, ocular melanoma occurs when there is uncontrolled reproduction of cells. When healthy eye cells develop certain kinds of mutations, they can multiply out of control, forming a melanoma.
Certain factors have been identified as increasing one's risk of developing ocular melanoma. These factors include having light-colored (blue or green) eyes, older age, and being Caucasian. Furthermore, certain inherited skin conditions such as dysplastic nevus syndrome may increase the risk for ocular melanoma.
Diagnosis & Tests
Ocular melanoma may be staged from one to four and tumor size is classified as either small, medium, or large. Diagnostic testing will involve eye examinations that require dilating the pupils. Tests that may be performed include a slit-lamp examination in which a microscope is used to examine the eyes, ophthalmoscopy which employs the use of a magnifying glass, and gonioscopy which uses a goniolens.
Once an ophthalmologist suspects that a melanoma may be present, additional testing may include an ultrasound, a test that utilizes high-energy sound waves which bounce off of internal eye tissues and helps create an image of the eye tissues from the sound wave's echoes. From these echoes, an ophthalmologist can determine the thickness of the melanoma. Another procedure, fluorescein angiography, consists of a dye injected into the arm which subsequently travels into the eye. Special camera equipment then takes pictures of the inside of the eye and helps determine whether any particular blockages are present.
Finally, a biopsy, a test in which a sample of tissue is removed from the eye to be tested in the laboratory, can be conducted in order to determine the presence of a melanoma, although this measure is usually unnecessary. Once an eye melanoma has been diagnosed, it is important to know whether the cancer has spread (metastasized), and imaging tests that scan the body may be conducted. These could include tests such as CT scans, MRIs, and PET scans.
Treatment & Therapy
Various treatment and therapy options exist to help treat ocular melanoma. The type of treatment chosen is dependent on numerous factors, including the location of the melanoma, the size of the melanoma, and the patient's general health. If the melanoma is small, the ophthalmologist may choose to monitor the melanoma to see whether or not it grows – which is termed watchful waiting.
Treatment may include surgical intervention, radiation therapy, and laser therapy. Radiation therapy makes use of high energy rays such as X-rays in order to kill the melanoma or at least to keep it from growing. Internal radiation therapy may be used in which radiation is delivered directly into or near the area being treated. External beam radiotherapy may be used as well; this type of radiation is delivered from outside of the body.
One type of internal radiation therapy is plaque radiation therapy. This form of treatment involves a disk, referred to as a plaque, that has radioactive pellets attached to it; this disk is placed on the wall of the eye where the tumor is located. Temporary stitches then help hold the plaque in place for a period of approximately 4 to 5 days, before removal.
Surgical intervention varies based on the size of the melanoma. Small melanomas often require the removal of the melanoma itself and some of the surrounding eye tissue, which is called a resection. Larger melanomas may necessitate enucleation, the removal of the whole eye. Exenteration involves the removal of the eye as well as all of the surrounding tissues of the eye including the muscles, nerves, and fat.
Prevention & Prophylaxis