Investigative Ophthalmology & Visual Science, Vol 37, 468-472, Copyright © 1996 by Association for Research in Vision and Ophthalmology

ARTICLES AND REPORTS

Structure-function correlations in the human medial rectus extraocular muscle pulleys

JD Porter, V Poukens, RS Baker and JL Demer
Department of Anatomy, University of Kentucky Medical Center, Lexington 40536-0084, USA.

PURPOSE. Fibroelastic pulleys function like the trochlea to fix the position and pulling direction of the recti extraocular muscles within the orbit. This study characterized the fine structure of the human medial rectus muscle pulley. METHODS. Human medial rectus muscle pulley tissue was dissected at autopsy, immersed in aldehyde fixative solution, and processed for and examined with light and electron microscopy. RESULTS. Pulley structure were located within posterior Tenon's fascia, closely surrounding the medial rectus muscle. Pulleys were comprised of a dense collagen matrix with alternating bands of collagen fibers precisely arranged at right angles to one another. This three-dimensional organization most likely confers high tensile strength to the pulley. Elastin fibrils were interspersed in the collagen matrix. Fibroblasts and mast cells were scattered throughout the relatively acellular and avascular collagen latticework. Connective tissue and smooth muscle bundles suspended the pulley from the periorbita. Smooth muscle was distributed in small, discrete bundles attached deeply into the dense pulley tissue. CONCLUSIONS. Fine structural observations confirm the existence and substantial structure of a pulley system in association with the medial rectus extraocular muscle. The presence of pulleys must be considered in models of the oculomotor plant. The cytoarchitecture and placement of pulleys suggest that they are internally rigid structures and are consistent with the idea that they determine functional origins for the extraocular muscles. However, the nature of the connective tissue-smooth muscle struts suspending the pulley system to the orbit supports the notion that the pulley position, and thus the vector force of the eye muscles, may be adjustable.

This article has been cited by other articles:

				J. L. Demer Inflection in Inactive Lateral Rectus Muscle: Evidence Suggesting Focal Mechanical Effects of Connective Tissues Invest. Ophthalmol. Vis. Sci., November 1, 2008; 49(11): 4858 - 4864. [Abstract] [Full Text] [PDF]

				G. P. Jaggi, H. R. Laeng, M. Muntener, and H. E. Killer The Anatomy of the Muscle Insertion (Scleromuscular Junction) of the Lateral and Medial Rectus Muscle in Humans Invest. Ophthalmol. Vis. Sci., July 1, 2005; 46(7): 2258 - 2263. [Abstract] [Full Text] [PDF]

				J. L. Demer Pivotal Role of Orbital Connective Tissues in Binocular Alignment and Strabismus The Friedenwald Lecture Invest. Ophthalmol. Vis. Sci., March 1, 2004; 45(3): 729 - 738. [Full Text] [PDF]

				R. Kono, V. Poukens, and J. L. Demer Quantitative Analysis of the Structure of the Human Extraocular Muscle Pulley System Invest. Ophthalmol. Vis. Sci., September 1, 2002; 43(9): 2923 - 2932. [Abstract] [Full Text] [PDF]

				S. Khanna and J. D. Porter Evidence for Rectus Extraocular Muscle Pulleys in Rodents Invest. Ophthalmol. Vis. Sci., August 1, 2001; 42(9): 1986 - 1992. [Abstract] [Full Text] [PDF]

				J. L. Demer, S. Y. Oh, and V. Poukens Evidence for Active Control of Rectus Extraocular Muscle Pulleys Invest. Ophthalmol. Vis. Sci., May 1, 2000; 41(6): 1280 - 1290. [Abstract] [Full Text]