Abstract
Silicone sponges were sutured to the sclera of owl monkeys to create an indentation which would simulate a tumor of the posterior segment of the eye. A tantalum clip inserted in the silicone sponge served as a marker for radiographic localization of the simulated tumors. The acute lesions obtained on the retina and choroid after moderately high doses of proton irradiation suggest that this method of aiming the proton beam will be adquate for human clinical trials.