Effect of the background on the disparity-induced ramp vergence response in humans.
OBJECTIVE
Our purpose was to investigate the changes in the dynamic property of vergence eye movements caused by changes in the co-existing stationary background in the central visual field.


METHODS
Disparity-driven target movement was presented virtually by a head-mounted liquid-crystal display. Two targets were used: a bar-shaped target that moved between 2 and 0.5 m along the mid-sagittal line at a speed of 50 cm/s (vergence target) and a background image of a cross-shaped target that stayed at a distance of 2 m (background target). Eight normal subjects participated in the experiments. The subject was asked to follow the vergence target while the configuration of the background target was randomly changed among four conditions in each experiment: the length (experiment 1) or the width (experiment 2) of the horizontal and vertical lines composing the cross of the background target was each randomly changed among four conditions. A limbus tracker was used to measure eye movements.


RESULTS
In experiment 1, there was a negative correlation between the amplitude of the vergence eye movements and the lengths of the lines of the cross in each of five subjects (mean r = 0.018, n = 48 in each subject). Similarly, in experiment 2, there was a negative correlation between the amplitude of the vergence eye movements and the width of the lines of the cross in each of 8 subjects (mean r = -0.12, n = 48 in each subject).


CONCLUSIONS
The vergence response to a target object significantly differs depending on the texture of background objects on the visual axis.
Division of Ophthalmology and Visual Science, Graduate School of Medicine and Dental Science, Niigata University, Niigata 951-8510, Japan. yhaya88-km@nifty.com
Yuuki
Y
Hayakawa
Mineo
M
Takagi
Atsuhiko
A
Iijima
Takehiko
T
Bando
Ritsuko
R
Takada
Atsushi
A
Miki
Tomoaki
T
Usui
Shigeru
S
Hasegawa
Haruki
H
Abe
D000328:Adult; D005133:Eye Movements / Q000502:physiology*; D006801:Humans; D010775:Photic Stimulation; D012016:Reference Values; D015357:Vision Disparity / Q000502:physiology*; D014794:Visual Fields / Q000502:physiology