saccades
Saccades are fast conjugate eye movements that refixate both foveas on a new target.1 The saccadic system corrects the position error between the target and the fovea, while the pursuit system matches eye velocity to target velocity.2
Saccades are rapid ballistic movements, with peak velocities of up to 700 degrees per second.1,3 Larger saccades reach higher velocities, and the consistent relationship among saccadic duration, peak velocity and amplitude is called the main sequence.3 Saccades must be fast to minimize the time during which foveation is not possible.1
Voluntary saccades are intentional movements toward a remembered target or during a search. Reflexive saccades respond to the sudden appearance of a target in the peripheral retina or to a sudden noise, and spontaneous saccades, which occur during speech or at rest in darkness, have no particular goal.1 The fast phases of optokinetic and vestibular nystagmus, the rapid eye movements of sleep and the corrective saccades during fast pursuit are also saccadic movements.2
More detail
When exploring a scene, people make two to three saccades each second, and about 200 milliseconds are needed to start a saccade toward an unexpected target.3 Even during steady fixation, a normal observer makes small saccades of a few minutes of arc, called microsaccades, without being aware of them.2
Sources (7)
- Liu, Volpe and Galetta, Neuro-Ophthalmology: Diagnosis and Management, ch. 16
- von Noorden and Campos, Binocular Vision and Ocular Motility, ch. 4
- Adler's Physiology of the Eye, ch. 8
- Bahill, A.T., Clark, M.R. and Stark, L. 1975. The main sequence, a tool for studying human eye movements. Mathematical Biosciences, 24(3-4), pp.191-204.
- Leigh, R.J. and Zee, D.S. 2015. The neurology of eye movements. 5th ed. New York: Oxford University Press.
- Rutstein, R. and Daum, K. 1997. Anomalies of Binocular Vision: Diagnosis & Management. St. Louis: Mosby.
- Sparks, D.L. 2002. The brainstem control of saccadic eye movements. Nature Reviews Neuroscience, 3(12), pp.952-964.
Reviewed October 2026