1. A method, of treating an eye, comprising: engaging an outer surface of an eye with an eye holder to maintain the eye in a substantially fixed position during a treatment period; communicating a signal, indicative of a position of the eye during the treatment period, from a sensor to an x-ray source; after engaging the outer surface of the eye, aligning the x-ray source with the eye by moving the eye with the eye holder; and based on the signal, emitting an x-ray beam from the x-ray source toward the eye to deliver therapeutic radiation to the eye.