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Invest Ophthalmol Vis Sci. 2012 Oct 25;53(11):7375-9. doi: 10.1167/iovs.12-9730.

Functional morphometry of horizontal rectus extraocular muscles during horizontal ocular duction.

Author information

1
Departments of Ophthalmology, David Geffen Medical School, University of California, Los Angeles, California 90095-7002, USA.

Abstract

PURPOSE:

We explored multiple quantitative measures of horizontal rectus extraocular muscle (EOM) morphology to determine the magnetic resonance imaging (MRI) measure best correlating with duction and thus contractility.

METHODS:

Surface coil coronal MRI was obtained in target-controlled central gaze and multiple positions of adduction and abduction in 26 orbits of 15 normal volunteers. Duction angles were determined by position changes of the globe-optic nerve junction. Cross-sectional areas, partial volumes, and location of peak cross-sections of the horizontal rectus EOMs were computed in contiguous image planes 2-mm thick spanning the EOM origins to the globe equator.

RESULTS:

All measures correlated significantly with duction angle (P < 0.0001). The best measures obtainable in single image planes were the maximum change in the cross-sectional area between equivalent image planes, with coefficients of determination R(2) = 0.92 for medial rectus (MR) and 0.91 for lateral rectus (LR), and percentage change in maximum cross-section with R(2) = 0.79 for MR and 0.78 for LR. The best partial volume measure of contractility was the change in partial volumes in four contiguous posterior planes (R(2) = 0.86 MR and for 0.89 LR), particularly when combined with the corresponding change in partial volume for the antagonist EOM (R(2) = 0.95 for MR and LR).

CONCLUSIONS:

EOM morphologic changes are highly correlated with degrees of duction and thus contractility. Both changes in single-plane maximum cross-sectional areas and posterior partial volumes provide accurate, quantitative measures of EOM contractility.

PMID:
22997285
PMCID:
PMC3481603
DOI:
10.1167/iovs.12-9730
[Indexed for MEDLINE]
Free PMC Article

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