Abstract
Fixating a small dot is a universal technique for stabilizing gaze in vision and eye movement research, and for clinical imaging of normal and diseased retinae. However, during fixation microsaccades and smooth “drifts” occur that presumably benefit vision by refreshing the retina and sharpening image perception. Yet microsaccades compromise image stability and usurp task attention. Motivated by evidence of similar control of microsaccades and catch-up saccades we ask if microsaccades are mitigated while fixating a peripheral target, since peripheral targets mitigate catch-up saccades during smooth pursuit. Human observers fixated either a small dot, the center of an 8-dot circular array (6° diameter), or a 9-dot composite stimulus. Microsaccade rate was significantly lower with the peripheral array (0.48 sac/sec) than the dot (1.0 sac/sec). However, reinserting the dot into the array increased microsaccade rate (0.72 sac/sec). Drift speed also decreased with the peripheral array, with and without the central dot (average 1.19 deg/sec), relative to the small dot (1.41 deg/sec). In contrast, eye position was more variable with the array than the dot alone or the dot plus array. The results suggest that analogous to pursuit of a foveal target, fixating a stationary one engages the saccadic system and compromises retinal image stability. In contrast, fixating a peripheral stimulus improves stability, thereby affording better retinal imaging and more attention for other tasks.