1. In an eye-position sensor which provides a signal representative of the X and Y coordinates of light reflected from the cornea of an eye; said eye-position sensor comprising: a substantially point source of light for illuminating the eye; and a light sensor including: a quadrantal array of contiguous photo detectors each of which generates a signal which is proportional to the illuminated area thereof; a lens for collimating the light from the point source of light reflected from the cornea of the eye, onto the quadrantal array of contiguous photo detectors; said light sensor characterized by: a spatial filter for providing a substantially rectangular pattern of light from said source which is specularly reflected from the eye onto the array so that each corner of the rectangular pattern lies in a different quadrant of the array; the filter being disposed so that movement of the eye changes the position of the pattern illuminating the array.