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Sei Yeul Oh, Vadims Poukens, Mark S. Cohen, Joseph L. Demer; Structure–Function Correlation of Laminar Vascularity in Human Rectus Extraocular Muscles. Invest. Ophthalmol. Vis. Sci. 2001;42(1):17-22. doi: https://doi.org/.
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purpose. Orbital and global layers of rectus extraocular muscles (EOMs) are believed to serve different functions. This study sought anatomic and functional evidence of differing blood flow in the two layers of rectus
methods. Four human orbits ranging in age from 17 months to 93 years were
serially sectioned and stained for muscle fibers with Masson’s trichrome and for vascular smooth muscle with monoclonal antibody to smooth muscle α-actin. Digitally assisted microscopy was used to
obtain measurements of luminal cross sections and counts of muscular blood vessels, as well as measurements of muscle fiber number and cross-sectional areas of the two layers. Findings were correlated with
first-pass gadodiamide contrast magnetic resonance imaging (MRI) in two
living humans to demonstrate relative perfusion of EOMs.
results. In all rectus EOMs, the orbital layer had significantly more vessels
per unit area, more vessels per fiber, and more total vascular luminal
area, than the global layer (P < 0.05). Vascularity of
EOMs was greatest in the youngest specimen. First-pass contrast MRI was
consistent with perfusion of the orbital layer earlier than the global
layer of living human rectus EOMs.
conclusions. Orbital layers of human rectus EOMs have significantly more muscular
vessels than the global layers and stain earlier after intravenous
bolus injection of paramagnetic MRI contrast. These findings suggest
higher and even more rapid blood flow in the orbital layers that may
correlate with greater metabolic activity. Greater blood flow is
consistent with more sustained mechanical loading of the orbital than
the global layer.
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