Overview

Botulinum toxin (BTXA) is a chemical that comes from bacteria (Clostridium botulinum). It is injected into the muscles around the eye to weaken them and change the eye position. BTXA has been used for squints since 1979.

Benefits of having BTXA

BTXA injections are useful in helping us to plan the surgical procedure that would give the best possible outcome for your eyes. Sometimes, it is recommended as another option to squint surgery. 

The advantage of BTXA is that it wears off. This means that if the treatment does give you troublesome double vision, it will not be permanent.

BTXA is most commonly used as a temporary treatment. However, it can sometimes be used repeatedly instead of squint surgery if an operation on the muscles would be difficult. This might apply if you:

• have previously had surgery
• have very small squints
• your condition might spontaneously change (so permanent surgery would not be recommended)

Sometimes, we use BTXA in people who cannot have a general anaesthetic but would still like their squint to be corrected.

Risks of BTXA injections

The treatment is safe and there is no risk of getting botulism poisoning. There is a small risk of an allergic reaction. Over 10,000 people throughout the UK have been treated with no long-term side effects.

Side effects

Like any treatment, BTXA has side effects but not everyone will get them. These side effects are almost always temporary and improve with time.

The most common side effect after an injection of BTXA is a droopy eyelid. This happens in about 1 in 20 injections. If this happens, the lid usually lifts within 2 weeks.

Sometimes there is bruising to the white of the eye.

There is an extremely rare possibility of the needle piercing the eye. The risk of this is no greater than 1 in 10,000 injections.

Medicine - Taking an unlicensed medicine

Most medicines used in the UK hold a product licence, granted by a government organisation. The product licence covers specific conditions in which medicine can be used to treat people. BTXA has never been covered by this licence, although it has been used in this way since 1979.

Your eye doctor thinks that BTXA should be used in this way, and is the most suitable treatment for your condition. We keep records of all injections in your medical notes. 

Read our information about unlicensed medicines. 

During the procedure

The surface of the eye is gradually numbed with a series of drops.

When the eye is numb, electrical leads are connected to your forehead. These allow the eye doctor (ophthalmologist) to position the needle correctly for the injection to be given. There will be a hissing sound while this is done.

When giving the injection, the doctor will gently hold your eyelids open and ask you to look in certain directions. The needle is kept in position for 30 seconds to prevent any BTXA from leaking, and then it is removed. You can blink normally during this procedure.

Pain during the procedure

You may be aware of a slight ache or dragging sensation during the procedure.

After the procedure

We put some antibiotic ointment in the eye, and then you can leave the hospital. We recommend you wear a pair of glasses, or sunglasses, after the appointment for about 1 hour, as your eye will still be numb. 

We suggest that you arrange for someone to accompany you home when you leave hospital.

You will usually notice no change for 1 or 2 days. After 3 to 5 days, the eye should start to move into a different position. As the BTXA wears off, the eye will start to turn back towards the middle.

It is useful if you can take photos of your eye position and write down your symptoms during this time. We can then work out the best eye position for you.

We usually arrange to see you 2 weeks after the first injection.

Double vision

Having double vision is an expected outcome of a BTXA injection, but it is not permanent. If this affects your work and normal activity, we can offer you some glasses with a film covering 1 lens.

It is important that you do not drive if you have double vision. For more information, visit the GOV.UK website. 

How long BTXA takes to wear off

A BTXA injection takes about 3 months to wear off completely. We do not usually do any surgery until it has completely worn off. It might be 6 months before more treatment or surgery is possible.