Term
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Definition
Smooth Pursuit
Saccade
Vestibulo-ocular
Vergence |
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Term
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Definition
Drift
Microsaccade
Physiological Nystagmus |
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Term
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Definition
Tracks slow moving objects uo to 40 degrees of arc per second.
Under very tight control.
Good pursuit eye movements are associated with good kinetic VA. |
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Term
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Definition
| Very fast movements. Occus when pursuit eye movement is in error, if detect motion in peripheral vision, or if you change fixation. Diseases that affect the fovea and neurological lesions can affect saccades. |
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Term
| Vestibulo-ocular eye movement |
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Definition
| Initiated by head or body motion detected by semicircular canals. Maintains fixation during head motion. Affected by vestibular disease or damage to the 8th nerve and other neural lesions. |
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Term
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Definition
| Eyes move in different directions (disjunctive eye movements). Tracks changes in 3rd dimension. Very slow. Neural control linked with accommodation and the iris. Tested with cover test. Affected by fatigue, alcohol, strabismus, diabetes and neurological lesions. |
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Term
| Tremor (Physiological Nystagmus) |
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Definition
| Very small movements and very fast. Not necessarily the same in both eyes. Results from mechanical tension between antagonistic muscles and does not affect perception. |
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Term
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Definition
| Moderate speed and very small. Stimulus is due to failure to hold fixation so acts randomly. |
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Term
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Definition
| very fast and very small. stimulus is to the prior drift. Purpose is to reposition the eye w/ respect to previous fixation. |
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Term
| Stabilized Imagery Experiment and Krauskopf experiment |
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Definition
Conclusions from both experiments:
1) Motion of an image on retina is needed for good vision;
2) information is coded by the information at the edge of a target and spilled in towards center of the object. |
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Term
Case Study:
How do baseball players play so well? |
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Definition
| To be a good batter, one needs to develop good smooth pursuit eye movements and learn to suppress their vestibulo-ocular eye movements. Requires good saccade as well as saccadic suppression. |
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