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JM Miller, JL Demer, V Poukens, DS Pavlovski, HN Nguyen, EA Rossi; Extraocular Tissue Type Architecture . Invest. Ophthalmol. Vis. Sci. 2002;43(13):1913.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: EOM pulleys (Miller, 1989) probably escaped earlier detection because they are distributed condensations of smooth muscle, elastin, and collagen, and because biomechanical modeling of the orbit (Miller, 1984; Robinson, 1975) had not yet predicted their existence. There have been few systematic attempts to characterize other distributed orbital structures that are able to show overall geometry and determine composition or mechanical properties of tissues. Characterizing distributed structures and properties requires an imaging approach, which unfortunately cannot directly give mechanical properties. Imaging can, however, give strong hints about mechanical properties and direct subsequent mechanical measurements by showing the types and densities of constituent tissues. Methods: We developed methods for producing 3D images of extraocular tissues, incorporating histochemical, immunohistochemical, and MRI results to distinguish striated muscle, smooth muscle, collagen, and elastin. Loss of registration of successive slices and distortion of the slices themselves were corrected by computer-aided image processing. We present results from several human cadaveric orbits as manipulable 3D objects so that spatial relationships and other distributed patterns can be appreciated. Results: In addition to connective tissue distributions that describe the most significant fascial constraints, we distinguish muscle lamina, blood vessels, and nerves (figure shows nerves - note, eg, that the neurofibrovascular bundle [Stager, 1996] takes a meandering path, and so is unlikely to exert effective extraocular elasticity). View OriginalDownload SlideView OriginalDownload SlideConclusion: Our data provide basic constraints on new biomechanical models, and on the theories of oculomotor physiologists and strabismologists, and will also be of interest to orbital surgeons generally.
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