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 injection.

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 available.
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.

Follow up
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 indefinitely.