Purchase this article with an account.
Kristina Irsch, David L. Guyton, Howard S. Ying; Different Mechanisms of Motor Fusion May Distinguish Patients with True Superior Oblique Paresis (SOP) from Those with Masquerading SOP. Invest. Ophthalmol. Vis. Sci. 2011;52(14):4698.
Download citation file:
© ARVO (1962-2015); The Authors (2016-present)
To determine the mechanisms of vertical fusional vergence in patients with superior oblique paresis (SOP).
We examined five patients with congenital unilateral SOP without previous muscle surgery, all able to fuse in straight ahead gaze or with a head tilt, with our custom tilting haploscope using 3-D video-oculography. Vertical fusional vergence was stimulated using concentric circle targets without torsional cues, subtending >54 degrees of visual angle. Eye movements were recorded during binocular and monocular viewing in straight ahead gaze with head straight and when tilted 45 degrees right and left. If the patient was unable to fuse the targets in the head-straight position, the targets were re-aligned so that the patient could barely fuse them.
With head fixed, either straight or tilted, four of the five patients showed the same pattern of torsional eye movements when overcoming their hyperdeviation with vertical fusional vergence: vertical vergence was accompanied by a cycloversion (torsion of both eyes in the same direction) towards the side of the hyperdeviation. The opposite mechanism of vertical fusional vergence was observed in one patient with head straight or tilted: vertical vergence was accompanied by a cycloversion away from the side of the hyperdeviation.
These mechanisms of motor fusion may be explained by avoidance of the apparent paretic superior oblique muscle in four patients and use of the oblique muscles in one patient. Different fusional mechanisms may thus help to differentiate between true SOP and other cyclovertical deviations of the eyes that mimic SOP. In addition, future investigation may reveal that the mechanism of motor fusion that a patient uses correlates with surgical outcome, and thus may influence the best approach to surgical correction.
This PDF is available to Subscribers Only