2020–2021 BCSC Basic and Clinical Science Course™
2 Fundamentals and Principles of Ophthalmology
Part V: Ocular Pharmacology
Chapter 16: Ocular Pharmacotherapeutics*
Purified Neurotoxin Complex
Botulinum toxin type A is produced from cultures of the Hall strain of Clostridium botulinum. It blocks neuromuscular conduction by binding to receptor sites on motor nerve terminals, entering the nerve terminals and inhibiting the release of acetylcholine. Botulinum toxin type A injections provide effective relief of the excessive, abnormal contractions associated with benign essential blepharospasm and hemifacial spasm. Cosmetic use of botulinum toxin, specifically in the treatment of glabellar folds, is popular as well. Botulinum is FDA approved for the treatment of strabismus; it may function by inducing atrophic lengthening of the injected muscle and corresponding shortening of the muscle’s antagonist (see also BCSC Section 6, Pediatric Ophthalmology and Strabismus, and Section 7, Oculofacial Plastic and Orbital Surgery).
Harrison AR. Chemodenervation for facial dystonias and wrinkles. Curr Opin Ophthalmol. 2003;14(5):241–245.
Issaho DC, Carvalho FRS, Tabuse MKU, Carrijo-Carvalho LC, de Freitas D. The use of botulinum toxin to treat infantile esotropia: a systematic review with meta-analysis. Invest Ophthalmol Vis Sci. 2017;58(12):5468–5476.
Khan JA, Steinsapir KD, McCracken M. Facial fillers, botulinum toxin, and facial rejuvenation. Focal Points: Clinical Modules for Ophthalmologists. San Francisco: American Academy of Ophthalmology; 2011: module 1.
Excerpted from BCSC 2020-2021 series: Section 2 - Fundamentals and Principles of Ophthalmology. For more information and to purchase the entire series, please visit https://www.aao.org/bcsc.