Rapid- and slow-velocity vergence eye movements. 1992

B Wick, and H E Bedell
University of Houston, College of Optometry, Houston, TX 77204.

Previously we have measured rapid-velocity vergence responses to targets at different distances that provided no disparity or accommodative stimulation. To evaluate the possibility that this rapid-velocity vergence occurs during saccades, the latencies of eye movement between two long dim luminous rods were compared under two conditions. Rapid-velocity vergence with an average latency of approximately 300 ms was elicited when subjects alternately viewed horizontal rods at distances of 38 and 78 cm, and with a vertical separation of 5.2 degrees. Horizontal saccades with a comparable latency were measured when the rods were equidistant and oriented vertically. The correlation between the mean latencies of vergence and saccadic movements was 0.97, suggesting that the two movements occurred together. In a second experiment vergence responses were measured when the subject looked between a bright vertical line on a screen at 76 cm and a second pair of lines (vertically displaced between 0.15 degrees and 3 degrees) with crossed disparity to simulate a target at 38 cm. Slow-velocity vergence often occurred alone when the vertical separation between targets was small; rapid-velocity vergence intruded when the separation between the targets was larger. The results can be accounted for if proximity and disparity stimulation act through a single vergence controller, the output of which produces slow- or rapid-velocity vergence depending upon whether the saccadic system is concurrently active.

UI MeSH Term Description Entries
D003290 Convergence, Ocular The turning inward of the lines of sight toward each other. Convergences, Ocular,Ocular Convergence,Ocular Convergences
D005133 Eye Movements Voluntary or reflex-controlled movements of the eye. Eye Movement,Movement, Eye,Movements, Eye
D006801 Humans Members of the species Homo sapiens. Homo sapiens,Man (Taxonomy),Human,Man, Modern,Modern Man
D000328 Adult A person having attained full growth or maturity. Adults are of 19 through 44 years of age. For a person between 19 and 24 years of age, YOUNG ADULT is available. Adults
D012438 Saccades An abrupt voluntary shift in ocular fixation from one point to another, as occurs in reading. Pursuit, Saccadic,Saccadic Eye Movements,Eye Movement, Saccadic,Eye Movements, Saccadic,Movement, Saccadic Eye,Movements, Saccadic Eye,Pursuits, Saccadic,Saccade,Saccadic Eye Movement,Saccadic Pursuit,Saccadic Pursuits
D013997 Time Factors Elements of limited time intervals, contributing to particular results or situations. Time Series,Factor, Time,Time Factor

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