Age-related macular degeneration is treated by radiation delivered from a miniature x-ray tube (20) inserted via a catheter(12) around the globe of the eye, to a position behind the macula (16). Methods are described for properly locating the catheter (12) and x-ray tube (20), using illumination on the catheter (12) and viewing through the front of the eye, or sensors on the catheter and a scanned beam shone from the front of the eye. Fluorescent excited by x-rays can also be used. Also described are methods and devices for immobilizing the probe once properly located in the eye, for standoff of the x-ray tube (12) from the target tissue, and for achieving prescription radiation dose in the choroid (22) while eliminating dose to adjacent tissues. The x-ray treatment can be enhanced using a radiosensitizing drug, and can be combined with PDT.