1. A system, for delivering radiation to an eye, comprising: an eye model, derived, at least in part, from anatomic data of a patient's eye; an emitter that delivers an x-ray beam to the eye with a maximum energy from about 10 keV to about 500 keV; a position guide, coupled to the emitter, that positions, based on the eye model, the emitter with respect to a location in or on the eye, to deliver the x-ray beam to a target in or on the eye; and a planning module that determines, based on the eye model, at least two parameters of treatment of the eye by the x-ray beam, and that outputs a signal indicative of at least one of the two parameters to the position guide or the emitter.