Suppression of Fixational Eye Movements

Abstract

Purpose: : Involuntary fixational eye movements or microsaccades are postulated to be essential for maintaining clear vision. Using eye movement monitoring, we established a method to suppress microsaccades in order to study visual function under saccade-free conditions.

Methods: : Subjects with normal vision participated in the study. Mechanical restriction was accomplished by fitting an eye coil (Skalar) attached to a handle that could be gently held on the eye without disturbing vision. Binocular eye movements were monitored and digitized using video ocular tracking technology (Eyelink1000) in two different visual conditions: 1) binocular fixation of a 0.5º dot and 2) both eyes in the dark. The frequency of the microsaccades was quantified and compared with control conditions.

Results: : The frequency of the microsaccades in the restricted eyes was reduced by more than 80 percent during binocular fixation conditions and more than 60 percent during dark conditions. The most notable finding is that microsaccades were similarly suppressed in the unrestricted eye in both conditions.

Conclusions: : The monocular mechanical damping has binocular suppression effects on microsaccades. We hypothesize that proprioceptive information plays a role in binocular suppression of microsaccades in dark conditions. This method of mechanical damping is an effective way of suppressing microsaccades while preserving visual function.

Keywords: eye movements: saccades and pursuits • eye movements: conjugate • visual acuity