A radioactive plaque looks a little like a contact lens, and measures about 12mm in diameter.
The plaque is made of metal and either Iodine-125 or Ruthenium-106 seeds. Radiation damages DNA in cancer cells so they cannot divide. When malignant cells are unable to replicate, cancer eventually dies.
The plaque is stitched to the surface of the eye. A continuous low dose of radiation is focused directly to the tumour for several days before the plaque is removed during a second surgery.
When Brachytherapy is Used
Radioactive plaques are used to treat solitary tumours measuring between 6-12 mm, located away from the macula (area of central vision) and optic nerve. In some cases, chemotherapy may be given to shrink the tumour before a plaque is applied.
What Treatment Involves
The plaque will be stitched to the surface of the eye under general anaesthetic. While the plaque is in place, your child will become radioactive. She may therefore be cared for in an isolated room for a few days, until the plaque is removed, again under general anaesthetic.
Your child may be given a lead patch to wear over the eye, to protect others from the radiation. If the eye being treated is your child’s only seeing eye, the patch may not be used, or may have a window in it to reduce anxiety and ensure maximum comfort during treatment.
Close contact with other people will be limited while the plaque is in place. However, one parent is usually permitted to stay in the isolation room. Children and pregnant women are not allowed to visit while the plaque is in place.
A plaque usually remains on the eye for two to five days. The exact length of time for your child will depend on the strength of plaque used (this decreases with the age of the plaque), and the size of the tumour being treated. This will be calculated by a nuclear physicist (an expert in medical radiation) before the first surgery.
For advice on helping your child cope with the time in isolation, click here.
After the Plaque is Removed
You will be free to leave the hospital as soon as your child is fully recovered from the general anaesthetic. Once the plaque is removed, your child will no longer be radioactive. You can mix with other people as normal, and all your possessions kept in the isolation room will be safe.
Your child may be prescribed eye drops and pain killers. Make sure you have these and know how to use them before you leave the hospital.
You will be given an appointment for an EUA in 3-4 weeks time. This time interval will enable the doctors to accurately assess how effective the plaque has been.
Too “hot” a plaque may cause damage to blood vessels that later react. This might cause bleeding in the eye.
The plaque will irradiate and kill normal cells in addition to the cancer cells. If the plaque is close to the centre of vision or the optic nerve, vision may be damaged.