Botulinum Toxin in the treatment of strabismus. A review of its use and effects

Abstract

Botulinum Toxin as a medical therapy was introduced by Dr Alan Scott more than 20 years ago. The first clinical applications of Botulinum Toxin type A (BT-A) were for the treatment of strabismus and for periocular spasms. Botulinum Toxin type A is often effective in small to moderate angle convergent strabismus (esotropia) of any cause, and may be an alternative to surgery in these cases. Botulinum Toxin type A may have a role in acute or chronic fourth and sixth nerve palsy, childhood strabismus and thyroid eye disease. The use of BT-A for strabismus varies enormously in different cities and countries for no apparent reason. Botulinum Toxin type A may be particularly useful in situations where strabismus surgery is undesirable. This may be in elderly patients unfit for general anaesthesia, when the clinical condition is evolving or unstable, or if surgery has not been successful. Botulinum Toxin type A can give temporary symptomatic relief in many instances of bothersome diplopia irrespective of the cause. Ptosis and acquired vertical deviations are the commonest complications encountered. Vision-threatening complications are rare. Repeated use of BT-A is safe.

Usefulness of Botulinum Toxin Type-A in the Treatment of Chronic Sixth Nerve Palsy

“…If the affected eye cannot be abducted beyond the mid-line, the transposition procedure will be required; if eye abduction is possible the recession and resection procedure should be sufficient. Botulinum toxin treatment was originally developed 25 years ago by Ala B. Scott to produce reversible weakening of extraocular eye muscle (chemodenervation) [2,13] in the treatment of strabismus. Today it is an important aid in the preoperative evaluation of possible postoperative diplopia on patients in which this cannot be done by means of prism or traction test; in acute paretic loss of ocular muscle function; when surgical treatment of the ocular muscles is not yet possible but the patient is obviously affected by diplopia or a forced posture of the head [2], in situations where strabismus surgery is not suitable (as in elderly patients unfit for general anaesthesia; when the clinical condition is evolving or unstable, or in case of unsuccessful surgery) [13], in acute Graves' disease, and especially into VI cranial nerve paresis [2], or in association with the surgery [14].…”

“…Botulinum toxin treatment was originally developed 25 years ago by Ala B. Scott to produce reversible weakening of extraocular eye muscle (chemodenervation) [2,13] in the treatment of strabismus. Today it is an important aid in the preoperative evaluation of possible postoperative diplopia on patients in which this cannot be done by means of prism or traction test; in acute paretic loss of ocular muscle function; when surgical treatment of the ocular muscles is not yet possible but the patient is obviously affected by diplopia or a forced posture of the head [2], in situations where strabismus surgery is not suitable (as in elderly patients unfit for general anaesthesia; when the clinical condition is evolving or unstable, or in case of unsuccessful surgery) [13], in acute Graves' disease, and especially into VI cranial nerve paresis [2], or in association with the surgery [14]. Depending on the surgical approach in VI nerve palsies, Botulinum toxin may be injected in the medial rectus muscle before muscle transposition surgery to loosen contracture [2] or, on the basis of our results, BTX-A injection can be considered an invaluable tool in the management and diagnosis of VI nerve palsy, and it allows differential diagnosis between paresis vs paralysis, which is the necessary condition to plan the correct surgical treatment and to obtain a successful functional outcome.…”

“…If diplopia is not adequately controlled it may require surgical treatment, the functional result of which is often however unpredictable. Botulinum toxin type-A (BTX-A) injected in the hyperfunctional muscles causes a flaccid paralysis by preventing the release of acetylcholine at the neuromuscular junction and thus results in a gradual physiological recovery of the hypofunctional muscles [5]. BTX-A injection can be used either during the waiting period for the spontaneous recovery or for surgery; in cases where VI nerve palsy is resolved, BTX-A help to prevent diplopia, whereas in the case of unresolved palsy, the toxin is an invaluable tool in the differential diagnosis between paresis versus palsy, which in turn allows the correct choice of surgical procedure.…”

Botox’s Place in the Complex Treatment of Oculomotor System Pathology (the Optimal “Portrait” of the Patient for the Chemodenervation)

“…[13], наиболее опыт-ными центрами международного уровня в области ис-пользования ботулотоксина-А в страбизмологии явля-ются группа во главе с Alan B. Scott из Сан-Франциско, The Toxin Clinic (Moorfields Eye Hospital, London) и оф-тальмологическая династия Gomez (Madrid). Впечатляет колоссальный опыт двух последних центров на период 2005 года: 18 000 и 7000 инъекций, соответственно.…”

Botulinum Toxin- An Allrounder in the Ophthalmologist's Pharmacopoeia.

“…Generally, it can be used as an alternative to surgery in non restrictive strabismus like small to moderate angle infantile esotropia, acute esotropia, post surgical residual and consecutive esotropia, and 6 th nerve palsy. 7,8,9,1 Other indications include patients with strabismus who cannot tolerate general anesthesia and cases with unpredictable surgical results like partially accommodative esotropias, esotropias in cerebral palsy and Thyroid eye disease. It has also been used in management of vertical deviations and nystagmus.…”