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Botox Treatment

What is botulinum toxin and how can it be used to correct a squint? How botulinum toxin injections can be performed in children and adults.

Video Transcript:

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

What is botulinum toxin and how does it work?

Botulinum toxin is a naturally occurring toxin produced by the bacteria Clostridia botulinum. It weakens muscles by disrupting the signalling between the nerve and the muscle.

When an electrical signal passes down the nerve to a muscle, a special chemical is released from the end of the nerve into the space between the nerve and the muscle. This chemical then attaches itself to receptors on the muscle cells and this in turn sends a signal to the muscle cells, causing them to contract.

Botulinum toxin works by sticking to these muscle receptors, so preventing the chemicals from attaching to them and as a result the muscle does not receive the signal to contract.

How long do the effects last for?

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.

How is botox treatment carried out?

In adults and cooperative teenagers botox treatment can be carried out in clinic using anaesthetic drops to numb the eye. Once the eye has been anaesthetised the botox can be injected directly into the eye muscle using a special needle connected to an electromyogram (EMG). 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 anaesthetic or using a ketamine anaesthetic. During a ketamine anaesthetic 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 anaesthetic 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.