Side effects can occur with any type of treatment for eye cancer, but not everyone has them or experiences them in the same way. Side effects of radiation therapy will depend mainly on the:
Radiation therapy damages cancer cells, but healthy cells in the treatment area can also be damaged, even though steps are taken to protect them as much as possible. Different cells and tissues in the body tolerate radiation differently.
Side effects can happen during, immediately after or a few days or weeks after radiation therapy. Most side effects go away after radiation therapy is over. Late side effects can occur months or years after radiation therapy. Some side effects may last a long time or be permanent. Side effects from radiation therapy to the eye may not show up right away.
Cataracts can develop after any type of radiation therapy to the eye. The lens of the eye becomes cloudy, which causes cloudy or foggy vision, trouble seeing at night or problems with glare from the sun or bright lights. It can take years for a cataract to develop after radiation therapy. If the cataract causes problems with vision, it can be removed by surgery.
An abnormality of the blood vessels in the retina (retinopathy) can develop because of external beam radiation therapy or brachytherapy to the eye. Whether retinopathy develops depends on the dose of radiation used and how close the treated area is to the retina. Retinopathy can cause loss of vision.
Radiation affects hair follicles, so people may lose their eyelashes with proton beam (charged particle) radiation therapy. Depending on the dose of radiation therapy, eyelashes may grow back after treatment. It will take some time for them to grow back. Sometimes this hair loss is permanent.
Sometimes the eyebrow can be affected as well, especially if the orbit of the eye is being treated.
External beam radiation therapy can cause dry eyes because of damage to the lacrimal gland, which produces tears. A shield may be used to protect the lacrimal gland and reduce this side effect.
Eye drops are used to moisten the eye if dryness becomes a problem. Dryness of the eye can sometimes develop as a long-term side effect. The person may need to use these drops every day.
Skin changes occur because external beam radiation therapy travels through the skin to reach the area being targeted for treatment. The skin in the eye area may become red or change colour. Redness usually lessens about 2 weeks after receiving radiation treatment. Some skin changes, like lightening or darkening of the skin around the eye, can be permanent. Some people do not experience any skin reactions with radiation therapy.
The cornea of the eye can be injured by radiation therapy to the eye, especially if the treatment area involves the cornea. Damage to the cornea may cause blurred vision. Depending on the dose of radiation used, this may be temporary and reversible. Larger doses of radiation may cause permanent blurred vision.
External beam radiation therapy to the eye can damage the optic nerve. This is not a common side effect, but can result in loss of vision.
External beam radiation therapy can block the flow of fluid within the eye, which causes the pressure within the eye to increase (glaucoma). Doctors may give medication (usually as eye drops, but sometimes as pills) to treat glaucoma while the person receives radiation therapy. This is usually a short-term side effect while receiving radiation therapy.