The Morphological Differences of Proprioceptors in Extraocular Muscles among Congenital, Acquired Exotropia and Congenital Nystagmus

ABSTRACT

PURPOSE: To evaluate morphological differences in proprioceptors in extraocular muscles between congenital exotropia, acquired exotropia and congenital nystagmus. METHODS: Nine medial recti including the myotendinous junction were resected using medial rectus resection in three congenital and five acquired exotropia patients. Two medial recti and two lateral recti were resected using the modified Kestenbaum procedure in two congenital nystagmus patients. The muscle tissues were examined under a light microscope following examination with a transmission electron microscope. RESULTS: In the congenital exotropia group, the electron microscopic findings showed degenerative changes in proprioceptors, such as decreased microtubules, axonal shrinkage and decreased myelin thickness. In the acquired exotropia group, the neural structures in the myotendinous junction were well maintained. There were no neural structures in the myotendinous junction in the congenital nystagmus group. CONCLUSIONS: Depending on the type of strabismus, there may be morphological differences in proprioceptors of extraocular muscles.