pursuits
Pursuits are smooth, voluntary eye movements that track a moving target and keep its image stabilized on the fovea.1 The pursuit system tries to generate eye velocities that match the target's speed, and pursuit stays accurate for targets moving at less than 50 degrees per second.2
Target motion across the retina produces a velocity error, the difference between target velocity and eye velocity, and that error drives the eyes after a delay of about 100 ms.1 With that delay, eye velocity always trails a changing target, and tracking grows inaccurate for targets moving at frequencies above about 1 Hz.1 Pursuit gain is the ratio of eye velocity to target velocity.3 When gain falls, the eyes fall behind the target and corrective catch-up saccades bring the foveae back on target.2,3
Pursuits are tested by having the patient follow a slowly moving target with both eyes.2 Pursuit and saccade pathways are distinct, and disease can impair one system and spare the other.2,3 Low pursuit gain commonly comes with aging and with medications, particularly tranquilizers and anticonvulsants, and cogwheeling is the most common neurologic abnormality of pursuit.3
More detail
Two parallel descending pathways drive pursuit.2 One starts at the occipitotemporal-parietal junction (area V5, homologous to monkey areas MT and MST), and the other starts in the frontal and supplementary eye fields.2 Both relay through the dorsolateral pontine nucleus and the nucleus reticularis tegmenti pontis to the flocculus, paraflocculus and vermis of the cerebellum.2 Supranuclear control of pursuit is ipsilateral, so the right occipitoparietal junction controls pursuit to the right.3
Pursuit is accurate below 50 degrees per second, maximum predictive pursuit velocities are about 60 degrees per second, and pursuit rarely exceeds 100 degrees per second, against 500 to 700 degrees per second for saccades.1,2,3 Normal pursuit latency is about 130 ms, shorter on average than the latency of saccades.3
Sources (9)
- Adler's Physiology of the Eye, ch. 8
- Liu, Volpe and Galetta, Neuro-Ophthalmology: Diagnosis and Management, ch. 16
- Scheiman and Wick, Clinical Management of Binocular Vision, ch. 13
- Barnes, G.R. 2008. Cognitive processes involved in smooth pursuit eye movements. Brain and Cognition, 68(3), pp.309-326.
- Krauzlis, R.J. 2004. Recasting the smooth pursuit eye movement system. Journal of Neurophysiology, 91(2), pp.591-603.
- 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.
- Spering, M. and Montagnini, A. 2011. Do we track what we see? Common versus independent processing for motion perception and smooth pursuit eye movements: A review. Vision Research, 51(8), pp.836-852.
- Thier, P. and Ilg, U.J. 2005. The neural basis of smooth-pursuit eye movements. Current Opinion in Neurobiology, 15(6), pp.645-652.
Reviewed October 2026