Pathologic Study of Supernumerary Orbital Band in Type I Duane Syndrome

Background/Aims: Accessory orbital bands are relatively rare and very few reports detail histopathology. Cases in the literature describe the composition of the bands as muscular and/or fibrous. The composition of the supernumerary band lying deep in the medial rectus muscle in a patient with type I Duane syndrome was investigated. Methods: Histochemical stains were used in conjunction with polarized light for differentiating compressed collagen from muscle. Immunohistochemistry was used for verification of the presence of muscle. Results: Compressed collagen appeared red using Masson trichrome staining. Collagen was positively identified by illumination with polarized light on several stains including the underutilized Sirius red dye. Conclusions: The findings of dense collagen fibers in the fibrotic band with focal striated muscle correlated with the restrictive strabismus. In concert with other cases in the literature, it is proposed that the fibrous bands are generally associated with restrictive strabismus. Bands that are muscular may or may not be associated with strabismus. Special techniques are needed to positively identify compressed collagen.