The present invention relates to an instrument and method for measuring the optical quality of an eye in a human subject. The instrument, which can be of either a single or double pass design and may include three-separate channels, permits real-time, simultaneous measurement of optical aberrations in the eye, retro-illumination of tear film to assess tear film stability, and scoring of psychophysical measures of visual performance. The simultaneous measurement of these parameters of optical quality and visual performance with the present instrument enables the operator to more accurately assess conditions and diseases of the eye, including dry eye disease (DED).
