J Korean Ophthalmol Soc.  2006 Feb;47(2):305-311.

Morphological Changes in Extraocular Muscle of Rabbit Eye Produced by Subtenon's Botulinum A Toxin Chemodenervation

• Ha BJ
• Kim YM
• Kwon HS
• Chang YH
• Han SH
• Chu YK
• Park JW
• Im CY

Abstract

PURPOSE: Currently, when injecting botulinum a toxin into the extraocular muscle, EMG (Electromyography) is used for accurate location. In this study, we examined the effects of subtenon botulinum toxin injection without EMG guidance by quantifying the morphological changes of the extraocular muscle fibers in rabbits.
METHODS
Using 10 New Zealand white rabbits, 10 units of botulinum a toxin in 0.1 ml of normal saline was injected into the subtenon space of the superior rectus muscles, 5 mm from the muscle insertion in right eyes. As a control, 0.1 ml of normal saline was injected into the subtenon space of the superior rectus muscles in left eyes. At 3 weeks after injections, the bilateral superior rectus muscles of each rabbit were carefully dissected from the globe. Cross-sections of 5 micrometer thickness were obtained at the site, 5 mm from the insertion of each superior rectus muscle. Sections were stained with Masson's trichrome and observed by light microscopy. Using Image-Pro Plus software, the diameter of the orbital layer myofibers was measured and statistical analysis was done using the Kruskal-Wallis test.
RESULTS
The average diameter of the orbital layer fiber cells after botulinum toxin injection was 11.5+/-2.26 micrometer at 3 weeks, whereas that of the control was 14.4+/-3.77 micrometer. The difference was statistically significant (p<0.01).
CONCLUSIONS
The diameter of myofibers in the orbital layer was reduced after subtenon botulinum a toxin injection. Further studies on the duration of botulium toxin in subtenon space and the change in the size of myofibers depending on the dosage of botulinum toxin will be necessary.

Keyword

Botulinum a toxin; Chemodenervation; Extraocular Muscle; Subtenon's injection

MeSH Terms

Botulinum Toxins
Botulinum Toxins, Type A*
Microscopy
Muscles
Nerve Block*
Orbit
Rabbits
Botulinum Toxins
Botulinum Toxins, Type A