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    Strabismus: Botox Treatment

    By John D. Ferris, FRCOphth
    Squint Clinic
    Pediatric Ophth/Strabismus, Strabismus

    Botulinum toxin, more commonly known as Botox, has been used to treat patients with strabismus since the 1970s and is an extremely safe and effective way of changing the position of the eyes.

    Botox starts to have an effect on muscles after 24-48 hours and has its maximum muscle weakening effect two weeks after treatment. The muscle will normally regain its normal function after 3-4 months. However, after repeat treatments the effect can be longer lasting. The reason why the effect of Botox wears off with time is because the muscle cells develop new receptors, so the signalling from the nerve to the muscle is restored.

    In adults and cooperative teenagers Botox treatment can be carried out in clinic using anesthetic drops to numb the eye. Once the eye has been anesthetized the Botox can be injected directly into the eye muscle using a special needle connected to an electromyogram (E

    MG). When the needle is in the correct position the patient is asked to move the eye so that muscle contracts and the EMG picks up the signal from the contracting muscle, so the ophthalmologist knows the needle is in the correct position. A very small dose of Botox (usually 0.1ml) is then injected into the muscle and the needle is removed after 30 seconds have passed. This pause before removing the needle minimises the spread of botox to surrounding tissues.

    In children Botox treatment is carried out either under a general anesthetic or using a ketamine anesthetic. During a ketamine anesthetic the eye muscles are still active and it is possible to use the EMG to locate the muscle in a similar way to adult treatments. If a general anesthetic is used a small opening is made in the conjunctiva beside the muscle so the surgeon can see where to inject the Botox. No stitches are needed to close this small opening.

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