Optokinetic response

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Horizontal optokinetic nystagmus.
Stare nystagmus for a random dot pattern moving from left to right.

The optokinetic response is a combination of a slow-phase and fast-phase eye movements. It is seen when an individual tracks (pursuit movement) a moving object with their eyes, which then moves out of the field of vision at which point their eye moves back to the position it was (saccade movement) in when it first saw the object. The reflex develops at about 6 months of age.[1]

Optokinetic nystagmus/response (OKN/R) is nystagmus that occurs in response to a visual stimulus on the retina. It is present in normally developed patients. The optokinetic response allows the eye to follow objects in motion when the head remains stationary (e.g., observing individual telephone poles on the side of the road as one travels by them in a car, or observing stationary objects while walking past them).

Eliciting optokinetic nystagmus[edit]

If an optokinetic drum is available, rotate the drum in front of the patient. Ask the patient to look at the drum as you rotate it slowly. With normal vision, an OKN response develops in infants and remains through adulthood. The OKN response consists of initial slow phases in the direction of the stimulus (smooth pursuits), followed by fast, corrective phases (return saccade). Presence of an OKN response in the temporal to nasal direction indicates an intact visual pathway. Another effective method is to hold a mirror in front of the patient and slowly rotate the mirror to either side of the patient. The patient with an intact visual pathway will maintain eye contact with herself or himself. This compelling optokinetic stimulus forces reflex slow eye movements.

OKN response can be used as an assessment of the infant to adult visual system{Casselbrant et al}, particularly in infants. When factitious blindness or malingering is suspected, check for OKN response in the temporal to nasal direction to determine whether there is an intact visual pathway.

Stereopsis development Motion stereopsis development (from 4-9 months of age) may be tested by comparing the quality of the monocular temporal to nasal tracking vs. the monocular nasal to temporal tracking in each eye. This is particularly helpful in infantile strabismus to determine if motion stereopsis development is present or not. Nasal to temporal motion tracking can be trained in infantile strabismus allowing for eye alignment (Baxtrom and Clopton, 2019) and may be associated with the Accessory Optic System for eye control (Brodsky et al. Arch Ophthalmol. 2012;130(8):1055-1059)through the accessory optic tract. Eye proprioception comes from Feldenstruktur fibers (Formation of Neuromuscular Junctions in Embryonic Cell Cultures Yutaka Shimada, D. A. Fischman, and A. A. Moscona doi:10.1073/pnas.62.3.715 PNAS 1969;62;715-721) and (JR Bruenech and IB Kjellevold Haugen Eye (2015) 29, 177–183) information providing a sensory feedback loop for eye position. If monocular pursuit tracking is symmetrical in each direction there is likely motion stereopsis developed.

See also[edit]

References[edit]

  1. ^ Atkinson J (1984). "Human visual development over the first 6 months of life. A review and a hypothesis". Hum Neurobiol. 3 (2): 61–74. PMID 6378843.

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