Involuntary movements of the eye during fixation and blinking.

SEVERAL authors have investigated recently the small movements of the eyeball which occur during fixation, by recording the movement of a beam of light reflected from the cornea itself (Lord and Wright, 1948), from a small drop of mercury on it (Barlow, 1952), or from a plane mirror on (Ratliff and Riggs, 1950; Ditchburn and Ginsborg, 1953) or attached to (Fender, 1955) a contact lens. These methods have all demonstrated the existence of fficks, originally observed by Adler and Fliegelman (1934), in which the eye rotates through a few minutes of arc in a few hundredths of a second. We have found that rapid movements of the eye may also be made apparent by viewing a slow running time-base on the face of a cathode-ray oscilloscope. The effect can conveniently be obtained by fixing the gaze on a vertical trace 5 to 10 cm. in length and of spot velocity 50 cm./sec. at a distance of 1 to 2 m. As would be expected, the trace generally has the appearance of a flickering straight line, but from time to time small transient deviations occur. Presumably, movements of the eye cause a displacement of the spot over the retina and the trace appears to be deviated in the opposite direction. Descriptions of the deviations were obtained from 24 observers. Usually the deviations corresponded to a rapid movement away from the line followed by a slightly slower return (Fig. 1). Their amplitude subtended from 4 to