Ultrastructural study of extraocular muscle tendon axonal profiles in infantile and intermittent exotropia.
OBJECTIVE
To investigate the ultrastructures of tendon axonal profiles in infantile and intermittent exotropia. Tendon axonal profiles are composed of myotendinous nerve endings that are presumed to serve as sensorial receptors in ocular proprioception.


METHODS
The study subjects included 10 patients with exotropia who had undergone surgery in one eye (recession and resection). They were divided into two equal groups. Five patients with infantile exotropia that had developed at under 12 months of age were allocated to group A. Another five, with intermittent exotropia that had developed at over 12 months of age, were allocated to group B. In all patients, medial recti were resected by 3-4 mm in order to obtain tissue samples, which were then examined under an electron microscope.


RESULTS
In group A, we noted many axonal degenerative findings, such as the retraction of axons from myelin sheaths with considerable shrinkage, axonal disintegration, and Schwann cell proliferation. On the other hand, we identified three unique findings in group B: intact axons with incomplete Schwann cell wrapping; intact Schwann cells not associated with axons, and disorganized Schwann cells with shrunken axons.


CONCLUSIONS
Different patterns of tendon axonal profiles were seen in association with the two types of exotropia. These differences may be related to the pathogenesis of these exotropia types.
Kim
Seung-Hyun
SH
Department of Ophthalmology, Korea University College of Medicine, Seoul, South Korea.
Yi
Sung-Tae
ST
Cho
Yoonae A
YA
Uhm
Chang-Sub
CS
D017668:Age of Onset; D001369:Axons / Q000648:ultrastructure*; D002648:Child; D002675:Child, Preschool; D005099:Exotropia / Q000473:pathology* / Q000601:surgery; D006801:Humans; D009469:Neuromuscular Junction / Q000648:ultrastructure*; D009801:Oculomotor Muscles / Q000294:innervation* / Q000648:ultrastructure; D009802:Oculomotor Nerve / Q000648:ultrastructure*; D013710:Tendons / Q000294:innervation* / Q000648:ultrastructure