Acute superior oblique palsy in monkeys: III. Relationship to Listing's Law.
OBJECTIVE
To investigate the three-dimensional orientation of the eye and its relationship to Listing's Law in monkeys with acute acquired superior oblique palsy (SOP).


METHODS
The trochlear nerve was severed intracranially in two rhesus monkeys. Three-axis eye movements (horizontal, vertical, and torsion) were measured with binocular, dual search coils during fixation of targets in a 40 degrees x 40 degrees grid. Rotation vectors were calculated, and Listing's plane (LP) was determined by a least-squares planar fit of eye torsion as a function of horizontal and vertical position.


RESULTS
The main findings were: (1) In the paretic eye, there was an immediate and sustained rotation of the orientation plane by approximately 25 degrees in the temporal direction; (2) the thickness of LP, defined as the torsional standard deviation (SD), increased little (by 0.13 degrees in M1 and 0.08 degrees in M2) after SOP, and (3) the SD of intrasaccadic torsion was slightly greater than that during fixation, but there was no change after SOP.


CONCLUSIONS
Acute SOP in rhesus monkeys leads to a temporal rotation of LP. This is consistent with a relatively increased extorsion in down gaze due to a loss of normal intorsion by the superior oblique muscle. The SD of torsion increased by only a small amount, implying that the validity of Listing's Law is not affected much by complete SOP, despite the large change in the orientation of LP.
Tian
Jing
J
Department of Neurology, The Johns Hopkins University School of Medicine, Baltiomre, Maryland, USA.
Shan
Xiaoyan
X
Zee
David S
DS
Ying
Howard
H
Tamargo
Rafael J
RJ
Quaia
Christian
C
Optican
Lance M
LM
Walker
Mark F
MF
D000208:Acute Disease; D000818:Animals; D005260:Female; D008253:Macaca mulatta; D009801:Oculomotor Muscles / Q000503:physiopathology*; D012399:Rotation; D012438:Saccades / Q000502:physiology*; D013285:Strabismus / Q000503:physiopathology; D014102:Torsion Abnormality / Q000503:physiopathology; D020432:Trochlear Nerve Diseases / Q000503:physiopathology*; D015348:Vision, Binocular / Q000502:physiology