Overview

Botulinum toxin (BTXA) is a chemical derived 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 for 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 an alternative to squint surgery. 

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

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

• who have had previous surgery
• with very small squints
• whose condition might spontaneously change (so permanent surgery would not be advised)

Sometimes we use BTXA in patients 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 developing botulism poisoning. There is a small risk of an allergic reaction. Over 10,000 patients 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 occurs in about 1 in 20 injections. If this happens, the lid usually lifts within 2 weeks.

Occasionally 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

The majority of 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.

The prescribing eye doctor thinks that BTXA should be used in this way, and is the most suitable treatment for your condition. Records of all injections are kept in the patient's 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 correctly position the needle for the injection to be given. There will be a hissing sound while this is done.

When they give the injection, your eyelids will be held open gently by the doctor, and you will be asked 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

Some patients are aware of a slight ache or dragging sensation during the procedure.

After the procedure

Some antibiotic ointment is applied to 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, so that we can work out the best eye position for you.

We normally arrange 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.

You should not drive if you have double vision. For more information, visit the GOV.UK website. 

How long it takes to wear off

It 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.