By Dr. Mark S. Siegel
Malignant “choroidal” melanomas arise from the blood-vessel layer “choroid” beneath the retina. In North America, 6 out of each million people will be diagnosed with a choroidal melanoma each year. Malignant choroidal melanomas can spread to other parts of the body.
Ophthalmologists can determine if you have a choroidal melanoma by performing a complete eye examination. This includes asking questions about your medical history, examining both of your eyes, looking into the eye through a dilated pupil at the tumor, performing an ultrasound examination, and specialized photography (to examine the circulation within the choroidal melanoma).
Your ophthalmologist will also request that you have a complete general medical check up and specific tests depending upon what they see inside your eye. Ophthalmologists can correctly diagnose an intraocular choroidal melanoma in over 96% of cases (without a biopsy). Though occasionally necessary, biopsies can be avoided because they require opening the eye (which risks letting choroidal melanoma cells out) and risk intraocular hemorrhage and infection.
Most patients with choroidal melanoma have no symptoms and the melanoma is found on routine eye examination. If patients have choroidal melanoma symptoms, they are usually seeing “flashes of light,” noticing “distortion” or loss of vision, and floating objects (floaters) in their vision.
1) If the choroidal melanoma is in the front of the eye (near the natural lens), it can push or tilt the natural lens causing an irregular astigmatism (blurring of vision).
2) Choroidal melanoma can leak fluid beneath the retina, making the retina detach and cause symptoms of flashing lights and floating specks.
3) If the choroidal melanoma is in the macula (center of vision), it can grow beneath the fovea making the patient far-sighted. The choroidal melanoma can also grow into and destroy the fovea causing distortion, loss of vision or changes in color perception.
It is important to note that most patients with choroidal melanoma have no symptoms at all. Their tumors are found when they visit their eye doctor for a “routine” eye examination. So everyone should have at least an annual eye examination (includingdilated ophthalmoscopy).
Other, more unusual presentations of anterior choroidal (iris) melanoma are discoloration of the iris, a brown spot on the outside of the eye, an irregularly shaped pupil and glaucoma.
Small Choroidal Melanoma:
Patients with a small choroidal melanoma can be treated after their first visit, but since growth helps to prove that the tumor is a cancer, your doctor may suggest “observation” or watching for a small amount of choroidal melanoma growth prior to treatment. Your ophthalmologist should discuss the relative risks and potential benefits of “observation for growth” as compared to “immediate treatment” for choroidal melanoma. Once growth is documented, your ophthalmologist will recommend definitive treatment.
Medium-sized Choroidal Melanoma:
Around the world, most patients with a medium-sized choroidal melanoma are treated with either radiation therapy or removal of the eye. Though there are several forms of eye and vision-sparing radiation therapy, ophthalmic plaque radiation therapy is the most common and widely used.
Since the results of the Collaborative Ocular Melanoma Study (COMS) suggest that plaque radiation therapy and enucleation of the eye are equally effective for the prevention of metastatic choroidal melanoma, few patients with medium-sized choroidal melanoma are treated by removal of the eye.
Because both enucleation and plaque radiation therapy for choroidal melanoma are likely to harm your vision (in that eye), you should discuss the risks and benefits of these and other treatment options in consultation with your ophthalmologist.
Large-sized Choroidal Melanoma:
A patient with a very large choroidal melanoma may be treated by removal of the eye (enucleation). This is because the amount of radiation required to destroy a choroidal melanoma that fills most of the eye may be too much for the eye
However, most patients with large-sized choroidal melanoma can also be treated with eye-sparing radiation therapy. After radiation for large choroidal melanoma, these eyes are at greater risk to have poor vision, to become uncomfortable and may have to be secondarily removed.
It is important to note that as compared to like-sized malignant melanoma of the skin, patients are much more likely to survive a choroidal melanoma. This is because it is much more difficult for a choroidal melanoma to spread from (get out of) the eye to other parts of the body. However, large (choroidal melanoma) tumor size decreases the chance that vision-sparing treatments will be successful. In general, the larger the choroidal melanoma the worse the prognosis for both vision
Patients often ask why they have a choroidal melanoma. Choroidal melanoma is more common among patients with blue vs. brown eyes, those with outdoor occupations and in Australia where there is an ozone hole. Therefore, it seems reasonable to assume (though unproven) that choroidal melanoma is related to sunlight (ultraviolet exposure).
Because sunlight exposure has been linked to several eye cancers and diseases of the eye, I suggest that you think of Sunglasses as Sun Block for your Eyes and start wearing your UV blocking sunglasses. They make great gifts too!