Botulinum toxin injection for squint in Adults

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What is Botulinum toxin?

Botulinum Toxin (BT) is a purified active compound Botulinum toxin A which is commercially sold by several different companies, and it is often known by its trade name, e.g. Botox®, Dysport® or Xeomin® etc. When injected into an eye muscle BT causes a temporary paralysis of that muscle.

What is the effect of BT and is it a one-off treatment?

Botulinum toxin causes a temporary, partial or complete, paralysis (weakness) of the muscle into which it has been injected. The effect starts after 1-2 days, reaches its maximum by one week and lasts approximately three months. Sometimes it is a one off treatment and sometimes a course of injections are needed. Your doctor will be able to explain which would be best for your child.

What is the role of BT for squints?

  • To improve the position or alignment of the eyes.
  • To assess the risk of causing permanent or troublesome double vision prior to squint surgery.
  • To correct double vision or a problem with the vision.
  • May be used in conjunction with squint surgery to enhance its effect.
  • To improve an abnormal head position.

How is the BT injection performed?

BT injection in adults is usually performed under local anaesthesia. Anaesthetic eye drops will be put in the eye(s) that you are having the injection. You will be asked to sit on a chair and small metal disks (skin electrodes) will be placed around your eye. The doctor will ask you to keep your head very still whilst only moving your eyes. The injection will be placed in the eye muscle and a loud sound will be heard (similar to an un-tuned radio). The needle will be left in place for 30 seconds. After the injection you will need to arrange a follow up appointment. Avoid bending or lifting heavy objects for 2 hours after the injection. Eye drops will be given after the injection to reduce the inflammation and prevent any infection.

What are the risks and side effects of BT?

Most side effects of BT are temporary and will resolve with time. Some of the side effects include:

  • Redness and irritation at the operation site.
  • Bruising around the eye affecting the lids
  • Under correction of the squint which may require a further injection
  • Sometimes the toxin may leak out and affect other eye muscles. This may result in the eye moving up or down (vertical misalignment of the eyes), which is usually temporary.
  • Drooping of the eyelid, this is usually temporary.
  • Permanent, unwanted change in the position of the eye after the injection has worn off. This is very rare and may require further treatment.
  • Extremely rara possibility of perforation of the eye by the needle which can result in the loss of eyesight from bleeding, infection, and retinal detachment. This risk is no greater than one in 5,000 injections.

When will I be seen again?

You will be seen again in the clinic 2 weeks after the procedure.

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