Abstract: An instrument for measuring aberration refraction of an eye is provided, having: a lens system defining an instrument optical axis and an alignment device for aligning the visual axis of the eye with the instrument optical axis. A light source (1) produces a probing beam that is projected through the lens system parallel to the instrument optical axis and is selectably positionable partially off-set from the instrument optical axis for entering the eye (15) parallel to the instrument optical axis at a plurality of locations on the cornea of the eye. A photodetector (19) measures the position of probing beam light scattered back from the retina of the eye to measure aberration refraction of the eye at a plurality of locations.