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Most eye cancers are melanomas (also known as ocular melanomas or intraocular melanomas).

Radiation therapy uses high-energy x-rays to kill cancer cells. It is the most common treatment for eye melanoma.

Radiation therapy can often save some vision in the eye, although sometimes vision might be lost if the radiation damages other parts of the eye. An advantage of radiation over surgery is that the eye structure is preserved, which can result in a better appearance after treatment.

Different types of radiation therapy can be used to treat eye cancers.

Brachytherapy (plaque therapy) for eye cancer

Brachytherapy (also called ocular brachytherapy or episcleral plaque therapy) is the most common radiation treatment for eye melanoma. Studies have shown that it is as effective as removing the eye with surgery (enucleation).

How brachytherapy works:

• A small carrier called a plaque is placed on the outside of the eyeball over the tumor.
• The plaque is shaped like a very small bottle cap with tiny radioactive seeds inside. It has gold or lead on the outside to shield nearby tissues from the radiation.
• The radiation travels a very short distance, so most of it will be focused only on the tumor.

How it’s done:

• The plaque is sewn onto the eyeball with tiny stitches during a short operation.
• Most people get general anesthesia (where you are in a deep sleep), but it can sometimes be done with local anesthetic (numbing medicine) and sedation.
• Most people will stay in the hospital while the plaque is in place—usually for at least a few days. The exact amount of time depends on the size of the tumor and the strength of the radiation source.
• At the end of treatment, another surgery is done to remove the plaque. Most people go home the day the plaque is removed.

It may take 3 to 6 months to see the full effect of the radiation on the tumor.

Brachytherapy cures about 9 out of 10 small to medium-size tumors. It can preserve vision in some people, depending on what part of the eye the melanoma is in. The outlook for vision is not as good if the tumor is very close to the optic nerve near the back of the eye, which carries visual images from the eye to the brain.

Proton beam radiation therapy for eye cancer

Proton beam radiation therapy uses a machine to focus a beam of radiation on a tumor. It’s different from standard external beam radiation therapy because it uses a beam of protons instead of x-rays. A proton beam delivers radiation to the tumor by releasing its energy at a specific distance, causing less damage to the healthy tissue it passes through.

For eye melanomas, proton beam radiation therapy might be a better option than brachytherapy if the tumor cannot be completely covered with a plaque because of its size, shape, or location. For example, it’s used more often for larger tumors or tumors close to the optic nerve. But not all cancer centers have the specialized machines needed for this treatment.

Getting treatment is much like getting an x-ray, but the dose of radiation is much higher. The treatment is not painful. In most cases, the total dose of radiation is divided into daily fractions over several days.

Stereotactic radiosurgery (SRS) or stereotactic radiation therapy (SRT) for eye cancer

These treatments are not used as often as brachytherapy or proton beam therapy as the initial treatment for eye melanomas. They are both used to deliver a large, precise radiation dose to the tumor area.

• Stereotactic radiosurgery (SRS) is done in a single session. Despite the name, there is no actual surgery involved in this treatment.
• Stereotactic radiation therapy (SRT) is done over a few sessions.

Different machines can be used to deliver radiation in one of two ways:

• Machines like Gamma Knife aim hundreds of thin, weak radiation beams at the tumor from different angles all at once. Each beam passes through healthy tissues with little damage, but together they focus a high dose on the tumor.
• Machines such as X-Knife, CyberKnife, and Clinac use a single, computer-controlled beam from a movable linear accelerator (a machine that creates radiation). Instead of many beams at once, the machine moves around the head, sending the beam in from many angles. This also allows a high dose to reach the tumor while limiting damage to healthy tissue.

Traditional external beam radiation therapy for eye cancer

Traditional external beam radiation therapy using wider beams of x-rays (photons) may be used in some situations, such as:

• After surgery to remove the eyeball (enucleation or orbital exenteration), if it appears that some cancer might not have been removed
• To help relieve symptoms from cancer that has spread to other parts of the body. This type of treatment is called palliative or supportive care

Possible side effects of radiation therapy for eye cancer

The main concern with radiation therapy is damage to parts of the eye. This can lead to problems such as:

• Blurry vision
• Dry eye
• Cataract (clouding of the lens of the eye)
• Retinal detachment
• Glaucoma (increased pressure inside the eye)
• Loss of eyelashes
• Problems with tear ducts
• Bleeding into the eye

Sometimes, treatments might result in partial or complete loss of vision or other problems, which might not happen right away and may worsen with time. The risk depends on the size and location of the tumor.

When the radiation is focused only on the affected eye, it is not likely to affect vision in the other eye or to cause other side effects sometimes linked with radiation therapy, such as hair loss or nausea.