Clinical correlations of aggrecan in the resected medial rectus muscle of patients with intermittent exotropia

The purpose of this study was to elucidate the role of extracellular matrix components such as aggrecan, fibronectin, and laminin in the extraocular muscle of patients with strabismus. Resected tissues of the medial rectus muscle of 47 patients with intermittent exotropia obtained during recession-resection surgery were frozen under liquid nitrogen and pulverized by a Freezer/Mill to solubilize the tissue for enzyme immunoassay. The total amounts of aggrecan, fibronectin, and laminin in the resected tissue were correlated with clinical data of patients such as age, exodeviation, and refractive error. The amount of aggrecan decreased significantly with the advance of age (P < 0.0001, Spearman rank correlation test), while the amount of laminin or fibronectin had no correlation with age. Patients with basic type intermittent exotropia showed larger, although not significantly, amounts of aggrecan than those with convergence insufficiency type (P = 0.0538, Mann-Whitney U-test). The amount of aggrecan may be related to motor aspects of intermittent exotropia.