Specializing in Pediatric Ophthalmology and Adult and Pediatric
About the Toxin
Botulinum toxin is a dichain protein produced by Clostridium
Botulinum. The organism can produce 8 strains of antigenically
different neurotoxins, with different toxicities in various
vertebrate species. The reason why they are produced is not
understood, as most clostridia are harmless anaerobic
saprophytes. We use only the A toxin formulation available from
Allergan (Botox) for strabismus treatment in the clinic.
All botulinum neurotoxins are taken up by the pre-synaptic
neuron at a cholinergic synapse. After an
interval (typically 2 days) the neuron becomes unable to produce
vacuoles containing acetylcholine, and the muscle it innervates
develops a flaccid paralysis. This paralysis changes the
alignment of the eye in the desired direction.
About the treatment injection
All injections are given with local topical anesthesia often
administered by the orthoptists. The patient is then connected
to the amplifier with stick on brow electrodes and the
injection electrode completes the circuit. The EMG signal is
heard during the injection confirming the position for the
After injection, the needle is left in position for a period of
30seconds, to permit diffusion into the muscle. After the
injection it is suggested that the patient has a choice of their
own glasses or a pad on can be placed over the eye fro an hour
to protect the anesthetic eye from foreign bodies, etc.
New patients are usually seen 1 or 2 weeks later. Old patients
attend at whatever interval allows them to maintain a
satisfactory ocular position, and they will usually have a good
idea what that is.
Complications and side-effects
These are detailed in the FAQ area under Botulinum Toxin which
you are requested to refer to as needed. A printed copy is
The commonest event is overcorrection and reversal of the
deviation. Patients often become very worried about this .
Please be reassured that the change is temporary and will
resolve in a few weeks. If double vision is a problem it can be
treated with a temporary patch over your glasses or eye. If
requested a stick on Fresnel prism may be helpful. A droopy
eyelid or "Ptosis" can occur secondary to diffusion of the
toxin to adjacent muscles. This will resolve over time.
Ocular perforation and retrobulbar hemorrhage are known major
complications are very rare and impairment of vision
secondary to these events even rarer. Your Doctor is an expert
in surgery and anesthesia about the eye and will be the one
performing the injection.
New patients are seen I or 2 weeks after injection. They may
need a “top-up” injection, occlusion, prisms, etc. The next
attendance sis typically 3 months later. Experienced long-term
patients have individualized regimens for treatment. Over an
extended treatment period, the interval between
injections may lengthen, and some patients, even when
non-binocular, may achieve long-term alignment, which persists