A comparison of the visual function of nictitation and blinking.

Abstract

Motion picture records indicate that in birds nictitation occurs regularly during saccadic head movements but rarely during pursuit or compensatory movements and that in human beings blinking occurs more frequently during saccadic eye movements than during pursuit or compensatory movements. These findings suggest that at least one function of nictitation and blinking may be to eliminate vision at those times when the visual image, if permitted to fall upon the retina, would necessarily be in rapid motion. Incidental observations indicate that movement of the visual image upon the retina constitutes a noxious stimulus for many organisms; numerous reflex mechanisms, including nictitation and blinking of the type described, appear to have the function of avoiding stimulation of this character.