Functional Anatomy of the Anophthalmic Socket: Insights from Magnetic Resonance Imaging

Detorakis, Εfstathios T.; Engstrom, Robert E.; Straatsma, Bradley R.; Demer, Joseph L.

doi:10.1167/iovs.03-0171

Cited by 38 publications

(23 citation statements)

References 29 publications

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“…In order to do this, the volumes of the medial rectus muscle (MRM), inferior rectus muscle (IRM), lateral rectus muscle (LRM), superior rectus-levator palpebrae superioris muscle complex (SRM-LPSM) and superior oblique muscle (SOM) were measured in T1W coronal images by summing the cross-sectional areas in every section and multiplying by the image plane thickness. Inferior oblique muscle (IOM) and optic nerve (ON) volumes were calculated similarly on T1W sagittal images, as described by Detorakis et al (10,11) (Fig. 2).…”

Section: Subjectsmentioning

confidence: 99%

Exploration of orbital and orbital soft-tissue volume changes with gender and body parameters using magnetic resonance imaging

Erkoç

Öztoprak

Gümüş

et al. 2015

Experimental and Therapeutic Medicine

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Abstract. The aim of the present study was to examine the total orbital volume (TOV) and total orbital fat volume (TOFV) in normal orbits in different age groups and to investigate the correlation of these measurements with age, gender and body parameters by magnetic resonance imaging (MRI). MRI data were acquired retrospectively from a total of 1,453 subjects divided into five age groups with 10-year intervals. The TOV and TOFV were measured using T1-weighted MRI for each subject and body parameters were also obtained. The measurements demonstrated that TOV increased with age and that the volume was larger in men than in women. While weight and height exhibited positive correlations with TOV in male and female subjects in the 20-29, 30-39 and 40-49-year-old age groups, only weight showed a positive correlation with TOV in female subjects in the 50-59 and 60-69-year-old age groups. However, TOFV increased by age in all groups and the increments were larger in women than in men. These results provide basic information about the effect of age, gender and body parameters on TOV and TOFV. The variations in TOV are associated with orbital soft-tissues changes rather than with TOFV.

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Section: Subjectsmentioning

confidence: 99%

Exploration of orbital and orbital soft-tissue volume changes with gender and body parameters using magnetic resonance imaging

Erkoç

Öztoprak

Gümüş

et al. 2015

Experimental and Therapeutic Medicine

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“…Not only does serial section histology show no such attachment, but also the sclera moves freely relative to pulleys transverse to the EOM axes. Anteroposterior rectus pulley movements persist even after enucleation [32], when the MR path inflection at its pulley continues to shift anteroposteriorly with horizontal versions, but the angle of inflection sharpens to as much as 90Њ at the pulley [32].…”

Section: Kinematics Of Pulleysmentioning

confidence: 99%

Mechanics of the Orbita

Demer

2007

Developments in Ophthalmology

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The oculomotor periphery was formerly regarded as a simple mechanism executing complex behaviors explicitly specified by innervation. It is now recognized that several fundamental aspects of ocular motility are properties of the extraocular muscles (EOMs) and their associated connective tissue pulleys. The Active Pulley Hypothesis proposes that rectus and inferior oblique EOMs have connective tissue soft pulleys that are actively controlled by the action of the EOMs' orbital layers. Functional imaging and histology have suggested that the rectus pulley array constitutes an inner mechanism, similar to a gimbal, that is rotated torsionally around the orbital axis by an outer mechanism driven by the oblique EOMs. This arrangement may mechanically account for several commutative aspects of ocular motor control, including Listing's law, yet permits implementation of noncommutative motility as during the vestibulo-ocular reflex. Recent human behavioral studies, as well neurophysiology in monkeys, are consistent with mechanical rather than central neural implementation of Listing's law. Pathology of the pulley system is associated with predictable patterns of strabismus that are surgically treatable when the pathologic anatomy is characterized by imaging. This mechanical determination may imply limited possibilities for neural adaptation to some ocular motor pathologies, but indicates greater potential for surgical treatments.

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“…Computational simulation suggests that forces required to implement anteroposterior pulley shifts are too great to be passive results of changes in tensions of the traversing EOMs [20]. Further, anteroposterior rectus pulley movements persist even after enucleation [24]. The inferior oblique pulley shifts anteroposteriorly by half of vertical ocular rotation [10], shifting its rotational axis similarly ( Fig.…”

Section: Kinematics Of Pulleysmentioning

confidence: 99%

Current concepts of mechanical and neural factors in ocular motility

Demer

2006

Current Opinion in Neurology

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Purpose of review-The oculomotor periphery was classically regarded as a simple mechanism executing complex behaviors specified explicitly by neural commands. A competing view has emerged that many important aspects of ocular motility are properties of the extraocular muscles and their associated connective tissue pulleys. This review considers current concepts regarding aspects of ocular motility that are mechanically determined versus those that are specified explicitly as innervation.Recent findings-While it was established several years ago that the rectus extraocular muscles have connective tissue pulleys, recent functional imaging and histology has suggested that the rectus pulley array constitutes an inner mechanism, analogous to a gimbal, that is rotated torsionally around the orbital axis by an outer mechanism driven by the oblique extraocular muscles. This arrangement may account mechanically for several commutative aspects of ocular motor control, including Listing's Law, yet permits implementation of non-commutative motility. Recent human behavioral studies, as well as neurophysiology in monkeys, are consistent with implementation of Listing's Law in the oculomotor periphery, rather than centrally.Summary-Varied evidence now strongly supports the conclusion that Listing's Law and other important ocular kinematics are mechanically determined. This finding implies more limited possibilities for neural adaptation to some ocular motor pathologies, but indicates possibilities for surgical treatments.

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Functional Anatomy of the Anophthalmic Socket: Insights from Magnetic Resonance Imaging

Abstract: Enucleation does not significantly change EOM volume, but shortens EOM paths, a change that would be expected to alter their mechanical properties. EOM pulleys appear to retain their functional role in enucleated orbits.

Cited by 38 publications

References 29 publications

Exploration of orbital and orbital soft-tissue volume changes with gender and body parameters using magnetic resonance imaging

Exploration of orbital and orbital soft-tissue volume changes with gender and body parameters using magnetic resonance imaging

Mechanics of the Orbita

Current concepts of mechanical and neural factors in ocular motility

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