title: Postulating a role for connective tissue elements in inferior oblique muscle overaction (an American Ophthalmological Society thesis).
abstract: OBJECTIVE
  To compare the localization and density of collagens I, IV, VI, and elastin, the major protein components of connective tissue, in the inferior oblique muscle of patients with overelevation in adduction and in controls and to characterize changes that develop following surgery. Biomechanical studies suggest that the connective tissue matrix plays a critical role in extraocular muscle function, determining tensile strength and force transmission during contraction.
  
  
  METHODS
  Prospective laboratory-based case-control study of inferior oblique muscle specimens from 31 subjects: 16 with primary inferior oblique overaction, 6 with craniofacial dysostosis, and 9 normal controls. Collagen I, IV, VI, and elastin were localized and quantified using immunohistochemical staining. Densities were compared using analysis of variance and post hoc comparisons.
  
  
  RESULTS
  In primary inferior oblique overaction, all connective tissue components in unoperated specimens were elevated compared to controls (P<.0001). Previously operated muscles showed normal levels of collagens IV and VI (P>.27) but increased collagen I. In unoperated craniofacial dysostosis specimens, only elastin was elevated (P=.03), whereas density of collagens IV and VI was lower in previously operated vs unoperated specimens (P=.015).
  
  
  CONCLUSIONS
  Elevated collagen and elastin levels in the cohort with primary inferior oblique overaction are consistent with the clinical finding of muscle stiffness. Contrarily, normal connective tissue densities in craniofacial dysostosis support the hypothesis that overelevation in this group reflects anomalous muscle vectors rather than tissue changes. Surgical intervention was associated with changes in the connective tissue matrix in both cohorts. These results have ramifications for treating patients with overelevation in adduction.
authors.affiliation: Department of Ophthalmology, University of Texas Southwestern Medical Center, Dallas, and Pediatric Ophthalmology & Adult Strabismus, PA, Plano, Texas (Dr Stager); Departments of Ophthalmology and Visual Neurosciences, and Department of Neuroscience, University of Minnesota, Minneapolis (Dr McLoon); and the Retina Foundation of the Southwest, Dallas, Texas, and Department of Ophthalmology, University of Texas Southwestern Medical Center, Dallas (Dr Felius).
authors.forename: David
authors.initials: D
authors.lastname: Stager
authors.affiliation: Department of Ophthalmology, University of Texas Southwestern Medical Center, Dallas, and Pediatric Ophthalmology & Adult Strabismus, PA, Plano, Texas (Dr Stager); Departments of Ophthalmology and Visual Neurosciences, and Department of Neuroscience, University of Minnesota, Minneapolis (Dr McLoon); and the Retina Foundation of the Southwest, Dallas, Texas, and Department of Ophthalmology, University of Texas Southwestern Medical Center, Dallas (Dr Felius).
authors.forename: Linda K
authors.initials: LK
authors.lastname: McLoon
authors.affiliation: Department of Ophthalmology, University of Texas Southwestern Medical Center, Dallas, and Pediatric Ophthalmology & Adult Strabismus, PA, Plano, Texas (Dr Stager); Departments of Ophthalmology and Visual Neurosciences, and Department of Neuroscience, University of Minnesota, Minneapolis (Dr McLoon); and the Retina Foundation of the Southwest, Dallas, Texas, and Department of Ophthalmology, University of Texas Southwestern Medical Center, Dallas (Dr Felius).
authors.forename: Joost
authors.initials: J
authors.lastname: Felius
mesh_terms: D000328:Adult; D000368:Aged; D002648:Child; D002675:Child, Preschool; D024042:Collagen Type I / Q000378:metabolism; D024141:Collagen Type IV / Q000378:metabolism; D024142:Collagen Type VI / Q000378:metabolism; D003238:Connective Tissue / Q000378:metabolism*; D004549:Elastin / Q000378:metabolism; D016326:Extracellular Matrix Proteins / Q000378:metabolism*; D005260:Female; D006801:Humans; D007124:Immunoenzyme Techniques; D007223:Infant; D008297:Male; D008875:Middle Aged; D009801:Oculomotor Muscles / Q000378:metabolism* / Q000601:surgery; D013508:Ophthalmologic Surgical Procedures; D013285:Strabismus / Q000378:metabolism* / Q000601:surgery
chemical_list: D024042:Collagen Type I; D024141:Collagen Type IV; D024142:Collagen Type VI; D016326:Extracellular Matrix Proteins; D004549:Elastin