What is a Choroidal Nevus?
Please see How the Eye Works for an introduction. Under the retina is a pigmented layer called the choroid. This layer is very rich in blood vessels, and is pigmented. The pigment in this layer is the same as in our skin. A choroidal nevus is a growth that arises from pigmented cells in the choroid. These are typically benign and are relatively common. Approximately 5% of people have at least one. They usually do not affect vision and so most people are unaware of their presence. It is most often detected during a routine dilated eye exam. In most cases, no treatment is necessary. Like moles on the skin, a choroidal nevus should be monitored to insure that it doesn’t change and grow. Features of the nevus can be very helpful to predict the risk of growth. These features include: the size and thickness, the presence of orange pigment, fluid leakage over the surface of the nevus, presence of drusen, and location within the eye. Larger and thicker nevi are commonly referred to as a suspicious nevus. These suspicious nevi need to be monitored most closely. If a nevus grows, it is very possible that it is a small melanoma. Even if a suspicious nevus does NOT grow, continued observation is very important. It is a misconception to assume that if it hasn’t grown in a few months, or even after a few years, that it will never grow.
What is the treatment for a choroidal nevus?
In most cases, no treatment is necessary other than periodic examinations. In addition to the eye examination itself, photographs and ultrasound evaluation to measure the thickness of the nevus are commonly done to accurately document the size and appearance of the nevus. The frequency of evaluations will depend on a number of factors including the appearance of the nevus, and how long it has been present, among other factors.
In some instances, the nevus may leak serum (the clear sticky part of blood), under the retina. If this leakage affects the central vision, than treatment of the leakage may be recommended. This is most often treated with laser photocoagulation or photodynamic therapy. Both are in office procedures
Retinal Photograph of an eye with a choroidal nevus (arrows)
Retinal Photograph of an eye with a malignant choroidal melanoma
Malignant “choroidal” melanoma arise from a layer under the retina called the choroid. Please see ‘How the Eye Works’ for more detailed description of the eye. In North America, about 6-7 out of each million people will be diagnosed with a choroidal melanoma each year. It is the most common eye malignancy that occurs in the eye. Malignant choroidal melanomas can spread to other parts of the body.
Most choroidal melanoma patients have no symptoms and the melanoma is found on routine eye examination. If patients have choroidal melanoma symptoms, they usually experience ﬂashes of light, distortion (bent or wavy lines) or loss of vision. None of these symptoms are specific for choroidal melanoma, but may be caused by a number of different eye conditions.
Ocular Oncologists 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 other specialized photography. A general medical check-up is also recommended and other testing depending on the results of your eye examination. Different than other parts of the body, an Ocular Oncologist can accurately diagnose a choroidal melanoma, without the need for a biopsy, in over 99% of cases.
Occasionally, it is necessary to perform a biopsy to confirm the diagnosis if the tumor appears unusual, or if it seems likely that it is a metastatic tumor (a tumor that has come from another part of the body to the eye) when there is no other known cancer in the person. Nowadays, biopsy of a choroidal tumor is done typically to perform genetic analysis of the tumor to determine prognosis. However, biopsy dose carry some risk of hemorrhage, infection, retinal detachment, and tumor seeding (outside the eye). Risks related to tumor seeding are thought to be very small. At this time, the results of the biopsy for genetic studies will not change the recommended course of treatment. However, this area of medicine is developing quickly and it is possible that the information may be helpful in the near future. Your ocular oncologist can review the pros and cons with you of this procedure.
Small Choroidal Melanoma
After a complete evaluation, treatment may be recommended. However, if the tumor is very small, a period of observation may be recommended to see if the tumor grows since growth helps prove that the tumor is a cancer and needs treatment. Your eye cancer specialist should discuss the relative risks and potential beneﬁts of “observation for growth” as compared to “immediate treatment” for choroidal melanoma. Once growth is documented, then treatment is typically recommended.
Medium-sized Choroidal Melanoma
Treatment of medium-sized melanoma typically involves a form of radiation. This can either be performed by placing a radioactive plaque on the eye (Iodine-125) or using a highly concentrated and focused radiation beam of protons. Both techniques are very successful at controlling the tumor and retaining the eye and at least some vision. Your ocular oncologist can review the pros and cons of these treatments as well as give you a better estimate of how the radiation treatment may affect your vision.
Large-sized Choroidal Melanoma
Most patients with large-sized choroidal melanoma can be also be successfully treated as well, though the prognosis for retention of vision usually is less optimistic. A patient with a very large choroidal melanoma may be treated by removal of the eye (enucleation). This is because the amount of radiation necessary to destroy a large choroidal melanoma may be too much for the eye to tolerate. In general, as the size of a melanoma increases, the chances for loss of vision with treatment and developing metastasis increase.
Following radiation treatment, it is important that the eye be examined regularly to insure that the melanoma has responded as expected. This typically requires fundus photography as well as ultrasonography. Usually, during the first 2 years following treatment, these evaluations are done every 4 months. Subsequently, evaluations are usually done every 6 months.
Also, it is important that systemic evaluation be done periodically to check for possible development of tumor spread (metastasis). The frequency of this evaluation and the type of testing is usually overseen by a medical oncologist and can be guided by results of the genetic evaluation of the tumor (if a biopsy was done).
Radiation Side Effects to the Eye
Radiation treatment can cause damage to the retina in the eye. In many cases, this is best managed with special treatments of a drug, such as Avastin, similar to how we treat patients with other retinal blood vessel diseases such as diabetic retinopathy or branch retinal vein occlusion. It has been our experience that this treatment is very helpful in treating radiation retinopathy, but does require regular care.
A more advanced type of radiation damage causes the growth of abnormal blood vessels on the iris. This can cause a very high elevation of pressure in the eye (Neovascular glaucoma). This is usually treated with laser treatment, though drugs such as Avastin may be used in conjunction.