Magnetic Resonance Imaging of Human Extraocular Muscles in Convergence
- 1 April 2003
- journal article
- Published by American Physiological Society in Journal of Neurophysiology
- Vol. 89 (4), 2072-2085
- https://doi.org/10.1152/jn.00636.2002
Abstract
Extraocular muscle (EOM) paths during asymmetrical convergence were evaluated by tri-planar, contrast-enhanced magnetic resonance imaging of the orbits of eight young adults during binocular fixation of a target aligned to one eye at 800 and 15 cm distance. Cross sections and paths of EOMs were determined from area centroids. In convergence, the aligned eye rotated and translated negligibly, while its inferior oblique (IO) muscle exhibited significant contractile thickening. There were no significant contractile changes in the cross sections of aligned eye rectus or superior oblique (SO) muscles in convergence. The converging eye rotated nasally 22.4° but translated negligibly. The converging eye medial (MR) and lateral rectus (LR) muscles exhibited large contractile cross-section changes, and the IO showed significant contractile thickening, while the vertical rectus muscles and the SO did not. Anterior paths of three aligned eye rectus EOMs could be determined in convergence and shifted consistent with a 1.9° extorsion of the rectus pulley array. Such extorsional reconfiguration of the rectus pulleys would move the pulleys in coordination with globe extorsion and avoid imparting torsional action to these EOMs. Extorsional rectus pulley shift in convergence is inconsistent with the reconfiguration predicted to explain the temporal tilting of Listing's planes, instead suggesting that this temporal tilting is due to variations in oblique EOM innervation. Absence of globe translation in convergence argues against overall EOM co-contraction. The reconfiguration of EOM geometry in convergence has important implications for single-unit studies of neural control.Keywords
This publication has 34 references indexed in Scilit:
- The Orbital Pulley System: A Revolution in Concepts of Orbital AnatomyAnnals of the New York Academy of Sciences, 2002
- Rectus extraocular muscle pulley displacement after surgical transposition and posterior fixation for treatment of paralytic strabismusAmerican Journal of Ophthalmology, 2002
- Magnetic resonance imaging after surgical transposition defines the anteroposterior location of the rectus muscle pulleysJournal of American Association for Pediatric Ophthalmology and Strabismus, 1999
- Heterotopic muscle pulleys or oblique muscle dysfunction?Journal of American Association for Pediatric Ophthalmology and Strabismus, 1998
- Summation of extraocular motor unit tensions in the lateral rectus muscle of the catMuscle & Nerve, 1997
- Relative Orientation of Primary Positions of the Two EyesVision Research, 1997
- Mathematics of three-dimensional eye rotationsVision Research, 1995
- Ocular translation and cyclotorsion due to changes in fixation distanceVision Research, 1980
- THE TORSION COMPONENT OF THE NEAR REFLEXOptometry and Vision Science, 1967
- THE DEPENDENCE OF CYCLOPHORIA ON CONVERGENCE. ELEVATION AND THE SYSTEM OF AXESOptometry and Vision Science, 1954