Incomitant Strabismus Does Extraocular Muscle Form Denote Function?

Department of Ophthalmology and Visual Sciences, University of Wisconsin-Madison, 53705, USA.
Archives of ophthalmology (Impact Factor: 4.4). 12/2010; 128(12):1604-9. DOI: 10.1001/archophthalmol.2010.301
Source: PubMed


The paradigm that an "underacting" extraocular muscle is always atrophic or hypoplastic and that an overacting extraocular muscle should always be enlarged leads to inconsistencies with clinical observations. These include findings of "overacting" inferior oblique muscles, superior rectus muscle overaction or contracture syndrome, and normal extraocular muscle diameters in patients with apparent superior oblique muscle palsy, among other clinical entities. These inconsistencies can be reconciled if one accepts the possibility that extraocular muscle contractile activity may reflect a change in neural input to an anatomically normal muscle or that muscle contractile activity may be altered by shifts in fiber type and distribution within a normal-sized muscle. This remodeling may result from vergence adaptation or from any change in neural stimulus to the muscle. There is substantial evidence to suggest that both of these theoretical possibilities may likely occur.

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    • "At present, no ideal experimental data can be used to determine this complicated constitutive relationship between active force and the stretch of an EOM because of the anatomical difficulty and ethical requirements, although a similar relationship of the skeletal muscle has been determined (Gordon et al., 1966) and has been widely used in the modern finite element modeling of muscles (Böl and Reese, 2008; Ehret et al., 2011). However, the fiber composition of an EOM is different from that of a skeletal muscle (Kushner, 2010); their biomechanical behaviors also differ (Quaia et al., 2009). To use the corresponding research results on the active force of a skeletal muscle in describing the active behavior of an EOM is inappropriate . "
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