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Printed at: 02:05:28 / 01-03-2021

Botulinum toxin treatment for squint / double vision

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What is Botulinum Toxin?
Botulinum toxin (Botox) is a drug that works by blocking nerve signals to muscles.

How is it used to treat squint/double vision?

It can be used in small amounts to weaken overacting eye muscles which have caused a change in eye position. In the treatment of squints, Botulinum injections can be used for three reasons:

1. They can be used to give the doctor additional information about a squint and help to decide if an operation would be useful.
2. They can be used to correct a squint if an operation is unsuitable.
3. They can be used to help improve double vision, caused by a squint.

How long does the effect last?
This can vary, but usually lasts for several weeks or occasionally months, before it will start to wear off. To begin with, you might notice a temporary reversal of the squint, followed by a gradual straightening of your eyes as the paralysis wears off.

What are the possible side effects?
• Temporary reversal of the direction of squint
• Temporary double vision – if this is significant and bothersome, you shouldn’t drive unless one eye is covered
• Temporary drooping of the eyelid on the injected side – this usually resolves after a few weeks
• Slight bruising of the surface of the eye

All these will improve without treatment. There is an extremely rare possibility of the needle perforating the eye.

Will it affect my general health?
The treatment is very safe and there is no risk to your general health. In particular, there is no risk of developing botulism or food poisoning. There is no known risk when the treatment is given to women who are pregnant or breastfeeding, but some patients prefer to postpone treatment until this is over.

What happens when I attend for the treatment?
1. First, you will see the Orthoptist who will check your vision and remeasure your squint.
2. Then you will see the Doctor who will explain the procedure and ask you to sign a consent form if you have not done so at a previous appointment.
3. The Orthoptist will put some anaesthetic eye drops in to reduce the discomfort during the injection. The injection can be slightly uncomfortable, especially if you have scar tissue due to previous
squint surgery.
4. The Orthoptist will attach some electrodes to your forehead so that we can accurately monitor the injection into the eye muscle.
5. The wires from these electrodes are then connected to an EMG machine. This detects very small levels of electrical activity from the muscles that move the eyeball. This helps the doctor to locate the correct site for treatment.
6. It is very important to stay still during this procedure and follow all instructions that you are given.
7. You will have an eye pad put on to protect the eye which you can remove after 2 hours.

What happens after the treatment?
• It takes 2-3 days for the effect of the Botox to start working and for the eye to begin to straighten.
• An appointment to measure the effect of the treatment will be made for 1-2 weeks.
• If you have any queries or concerns after your treatment please contact the Orthoptists on 01908 995532.

If required, references can be supplied for the information contained within this leaflet from the Ophthalmology Department.