Microsaccade

The term microsaccade describes a rapid, jerky gaze target movement of the eye with a very small amplitude between 3 and 50 angular minutes . The maximum speed of the movement is linearly dependent on the distance covered and is approximately 8 degrees / s with an amplitude of 5 angular minutes, 80 degrees / s with an amplitude of 50 angular minutes. In addition to slow drifts and micro-tremors, micro- saccades are part of what are known as micro-movements, which are counted as eye movements . They are used to regularly realign the lines of sight to a point of fixation, from which they constantly deviate by means of drifting movements, so as not to trigger any local adaptation .

Microsaccades typically occur 1 to 3 times per second, but their rate varies widely between people. In naive test persons, their amplitude is usually less than 30 arc minutes (typically <15 arcmin. This angle corresponds to approx. 80 µm or ≈ 40 photoreceptor displacement on the retina ). It is currently assumed that the generation of microsaccades and saccades are based on similar processes and shared neuronal structures.

Physiological importance

The receptors of the retina mainly react to changes in light conditions. A constant light stimulus leads to loss of vision due to receptor fatigue, resulting in the impression of self-gray (local adaptation). If the head is fixed and the eye muscles are paralyzed, temporary blindness occurs . Micro-movements of the eye constantly shift the light falling on the retina to various receptors and thus enable vision . Microsaccades seem to play a role here, especially for peripheral vision (seeing in the corner of the eye), since the receptive fields of the retinal cells there are too large to achieve changes in stimuli due to other micro-movements.

See also

• Eye movements
• Visual perception

Individual evidence

1. ↑ Most naturally occurring human saccades have magnitudes of 15 degrees or less. A. TERRY BAHILL, DEBORAH ADLER, AND LAWRENCE STARK. | http://www.iovs.org/cgi/reprint/14/6/468.pdf
2. ^ Martin Rolfs: In-between fixation and movement: On the generation of microsaccades and what they convey about saccade generation.

literature

• Herbert Kaufmann: Strabismus . With the collaboration of W. de Decker et al., Stuttgart: Enke, 1986, ISBN 3-432-95391-7

Web links

• Ute Dürrwächter: Analysis of the eye movements of children with reading and spelling disorders . Dissertation, University of Tübingen, 2003 (PDF file; 2.32 MB)