Hyperthermic Treatment of Intraocular Tumors

A 5.8-gigahertz (GHz) ophthalmic microwave applicator was used to treat choroidal melanoma (Greene strain) in rabbits. High-frequency electromagnetic radiation provides a favorable dose distribution to induce local hyperthermia in the treatment of intraocular tumors. Heating of the neoplasm, while sparing normal ocular structures, is best accomplished by a transscleral approach. A hyperthermia plaque is placed on the sclera at the base of the intraocular tumor. Contact (resistive) heating and electromagnetic radiation (radiofrequency and microwave) are best suited to a plaque technique. The advantages of electromagnetic heat induction, as compared with contact heating, are twofold: The depth of hyperthermic penetration can be modulated by frequency selection, and the tissues with low water content (sclera) remain relatively unaffected by microwaves. The 5.8-GHz ophthalmic microwave applicator satisfies the requirements for local hyperthermic treatment of intraocular tumors.