System for detecting the retinal ischemia of a patient and method of determining a signal indicative of whether the blood flow within the eye of a subject is impaired, the method comprising the steps of: providing a hand-held device having a light source, a light diffuse reflector and at least one electrode； positioning the device such that the at least one electrode contacts the skin of the subject proximate the eye； activating the light source to direct light towards the eye of a subject, wherein the light diffuse reflector redirects the light to provide a substantially even illumination to the retina of the eye； establishing the intensity of the light source based upon the area of the pupil of the eye so that the light stimulus to the retina of the eye is constant； determining the diameter or area of the pupil of the eye； detecting an electrical signal by the at least one electrode responsive to the stimulation of the eye by the light； and determining said signal indicative of whether the blood flow within the eye is impaired by using a signal indicative of activating the light source and the electrical signal detected by the at least one electrode.
