The best way to prevent metastatic melanoma is to destroy the primary intraocular cancer during the first treatment. Dr. Finger explains why the American Brachytherapy Societry Eye Plaque Guidelines defines normal plaque placement as covering the entire tumor and at least a 2-3 mm free margin of normal-appearing tissue. In order to make sure that happens, it is important to make sure all the muscles on the outside of the eye are temporarily moved away from the plaque. Simply, the radiation plaque should not be pushed to the side or lifted away from the eye by an extraocular muscle. Even if the patient has secondary double vision that must be later fixed, it is better than local regrowth that has been proven to be associated with a 6.3 Hazard of metastatic disease.