Dissociated vertical deviation: head and body orientation affect the amplitude and velocity of the vertical drift.
OBJECTIVE
Five subjects with dissociated vertical deviation (DVD) were studied to determine if the amplitude or velocity of the vertical components of the DVD were affected by head/body orientation with respect to gravity.


METHODS
Deviations were measured in head upright, head supine, and supine positions, with head hanging postures using a binocular CCD video-based infrared eye tracker. Subjects were required to fixate a target presented in the primary position during alternate or cover/uncover tests.


RESULTS
Amplitude and velocity of DVD both in onset and recovery were affected by head/body orientation with respect to gravity. In four of five subjects, the amplitude of the DVD was asymmetric between the two eyes when the head was upright. When the head/body was moved from an upright to a supine with head hanging backward condition, the amplitude of the DVD in the two eyes inverted. The eye with the larger DVD in the upright position had a smaller DVD in the head-hanging orientation. A similar relationship existed between velocity and head/body orientation. We found that DVD velocity increased with amplitude.


CONCLUSIONS
Passive effects of gravity on the eye-inorbit do not influence DVD magnitude or frequency of occurrence. The data suggest, however, that otolithic and possibly neck afferent inputs play a role in DVD magnitude and may be a part of the etiology of the condition.
Goltz
H C
HC
Department of Psychology, York University, Ontario, Canada.
Irving
E L
EL
Hill
J A
JA
Kraft
S P
SP
Steinbach
M J
MJ
D000328:Adult; D004585:Electrooculography; D005133:Eye Movements / Q000502:physiology*; D005260:Female; D006112:Gravitation; D006257:Head; D006801:Humans; D008297:Male; D008875:Middle Aged; D015835:Ocular Motility Disorders / Q000209:etiology / Q000503:physiopathology*; D009949:Orientation / Q000502:physiology*; D011187:Posture / Q000502:physiology*