Structure-function correlation of laminar vascularity in human rectus extraocular muscles

• Published in: Investigative ophthalmology & visual science Vol. 42; no. 1; pp. 17 - 22
• Main Authors: SEI YEUL OH, POUKENS, Vadims, COHEN, Mark S, DEMER, Joseph L
• Format: Journal Article
• Language: English
• Published: Rockville, MD Association for Research in Vision and Ophtalmology 2001
• Subjects: Adult; Aged; Aged, 80 and over; Biological and medical sciences; Blood Flow Velocity; Blood Vessels - anatomy & histology; Cell Count; Child, Preschool; Eye - anatomy & histology; Eye - blood supply; Eye and associated structures. Visual pathways and centers. Vision; Fundamental and applied biological sciences. Psychology; Humans; Infant; Magnetic Resonance Imaging; Male; Middle Aged; Muscle Fibers, Skeletal - cytology; Muscle, Smooth, Vascular - cytology; Oculomotor Muscles - blood supply; Oculomotor Muscles - physiology; Orbit - anatomy & histology; Orbit - blood supply; Vertebrates: nervous system and sense organs; Human; Rectus lateralis muscle; Rectus inferior muscle; Muscular fiber; Orbit(eye); Layer; Nuclear magnetic resonance imaging; Blood flow; Vascularization; Eye; Visual system; Rectus medialis muscle; Cadaver; Comparative study; Rectus superior muscle
• ISSN: 0146-0404; 1552-5783

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 EOMs. 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 alpha-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. 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. 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.