Mikrosakkader

Mikrosakkader, known in English as micro-saccades, are small, rapid, involuntary eye movements that occur when a person attempts to fixate on a visual target. Their amplitude is typically a fraction of a degree of visual angle, commonly around 0.2 to 1 degree, with durations of tens of milliseconds and peak velocities that can reach several tens to hundreds of degrees per second.

These movements arise from the same oculomotor circuitry that generates larger saccades, involving brain structures such as the superior colliculus and brainstem saccade generators. Their timing is regulated in part by omnipause neurons, and they are recorded as part of the broader category of fixational eye movements, which also includes drift and tremor.

The primary function of mikrosakkader is to prevent perceptual fading of the stationary image on the retina by periodically refreshing the retinal input. They may also play a role in fine spatial sampling and in directing attention, with the direction and occurrence of micro-saccades sometimes linked to the locus of covert attention. Their rate and characteristics can be modulated by cognitive factors, such as attention and mental load, as well as by the visual properties of the scene.

Measurement and study of micro-saccades rely on high-resolution eye-tracking techniques. Video-based trackers with high sampling rates or scleral search coils are used to detect these small, rapid movements and distinguish them from drift and tremor. In research, mikrosakkader are a standard measure of fixation stability and are used to investigate links between eye movements, perception, and attention; clinically, interpretations are cautious, and alterations in micro-saccade metrics are an area of ongoing study rather than a standalone diagnostic criterion.