Monocular fixation in human eye movement

Abstract

The monocular eye movements associated with the maintenance of fixation have been recorded using the contact lens/optical lever system. The records, in analogue form on magnetic tape, were subsequently converted to a digital form and analysed on a computer. It is found that there is reasonable agreement between the responses of the same subject on different days, Analysis of the magnitudes and preferred directions of saccades and drifts and their interrelationships show that there is an elliptical overall fixation area which is subdivided into a series of overlapping short-period fixation areas. The results indicate that saccades occurring during fixation have one of two functions, either ( a ) to recentre the retinal image on the short-period mean fixation position, or ( b ) to move the short-period fixation area, possibly to avoid retinal receptor fatigue. An organizational model of the fixation control system has been developed from the analysis of results.