Botulinum toxin: a treatment for squint
Information for patients from the Orthoptic Department
This leaflet explains the following.
What botulinum toxin is.
How it is used to correct a squint.
How long the paralysis lasts for.
What happens during and after treatment.
We hope this leaflet answers some of the questions you may have. If you have any further questions or concerns, please speak to your orthoptist.
What is botulinum toxin?
Botulinum toxin is a chemical, which temporarily paralyses the muscle into which it is injected.
How is it used to correct squint?
When it is injected into the relevant eye muscle, botulinum toxin causes a temporary correction of a squint.
How long does the paralysis last?
The injection takes 1 to 4 days to take effect. The effect of the injection usually lasts for 3 to 4 months, but each patient is different. It then gradually wears off completely.
When can the injection be given?
Before squint surgery, to assess any risk of double vision following surgery.
As an alternative to squint surgery, if:
a patient is unfit for general anaesthesia; or
for small squints, where there is a risk of over correction.
As an addition to squint surgery.
To help with double vision and recovery in patients with eye muscle palsies.
Are there any alternatives?
If you have diplopia (double vision), prisms can be a non-invasive alternative to botox. Prisms are typically used in the first instance to relieve symptoms. They can be used as long-term relief for double vision.
Squint surgery is also an alternative. However, most patients will need a botox injection before surgery, to assess their risk of developing double vision afterwards.
These treatments will be discussed with you before any decisions are made.
What will happen if I refuse treatment?
It is your choice whether you have treatment or not.
If you choose not to have botox, and you have diplopia (double vision):
you may continue to be monitored in the Orthoptic clinic and be corrected with a prism; or
we may discharge you to the care of your optometrist. The orthoptist can look into incorporating the prism into your glasses.
You can be referred back to our service by your GP or optician, if you change your mind in the future.
How do I prepare for my injection?
If you take blood thinners, please tell your consultant. You may need to stop taking these a few days before your procedure.
If you wear contact lens, do not wear them for 48 hours before your treatment.
Please make sure you remove any eyelash extensions or false lashes before your procedure.
Make arrangements for someone to pick you up and drive you home. Do not drive home after your procedure. If you have any problems getting home after your procedure, please tell your orthoptist.
Where is the procedure carried out?
The treatment is carried out as an outpatient in the Eye Clinic at Kent and Canterbury Hospital (K&C).
What happens when I arrive at the hospital?
Please report to the Eye Clinic at K&C for your first orthoptic examination. You will discuss the procedure with your consultant and sign the consent form. If you have any questions or concerns, please ask them at this appointment.
Why do I need to sign a consent form?
All patients must give permission before they receive any type of:
medical treatment
test; or
examination.
Consent is usually given when you sign the consent form before your treatment. We may ask you to give your consent verbally (spoken rather than written consent).
You must give your consent voluntarily.
The hospital must give you all the information you need to make a decision about your treatment. This is so you can give us informed consent. Please speak to staff if:
staff have not given you this information; or
they have but you still have questions.
You must be capable of giving consent. This means you understand the information given to you, and can make an informed decision.
When we ask you to give consent, please use this time to ask any questions you may still have. For more information, please go to the NHS Consent for Treatment web page. Remember, you can withdraw your consent for treatment at any time.
What happens during my procedure?
Before your procedure, local anaesthetic drops are used to numb your eye.
You will need to lie still on a couch for approximately 10 minutes during the procedure.
Electrode wires are placed on your forehead and connected to an amplifier and loudspeaker. This allows the exact site of the injection to be carefully monitored.
You will hear a loud noise from the loudspeaker and the medication is injected. We will demonstrate this noise by asking you to screw your eyes closed before the injection, so you know what to expect.
The injection will be held in place for 30 seconds.
Occasionally, we may inject more than one muscle. We will agree this with you before your procedure.
If your consultant needs to review your response, they may ask you to stay in hospital for 10 to 20 minutes after your injection. Most patients do not need a review and are able to leave when they feel ready.
How long will I have to stay in hospital?
Most patients are in the department for 1 to 2 hours.
Are there any risks to having the treatment?
This treatment is extremely safe in treating squint.
There is no risk of developing botulism.
This procedure involves a needle being inserted near the eye. Because of this, there is a very small risk that the needle will perforate the eye. This happens during 1 in 650 injections at most. If this happens, it can lead to a retinal detachment, and you will need further treatment. [1]
Will I have to wear a patch after my injection?
Not if you normally wear glasses. The local anaesthetic drops take 2 to 3 hours to wear off. The glasses will help you to not scratch or rub your eye during this time.
If you do not wear prescription glasses, we advise you to:
bring a pair of sunglasses with you to your appointment; or
you may need to wear an eye shield.
Will I be able to drive home?
Do not drive home after your procedure. Make arrangements for someone to pick you up and drive you home. If you have any problems getting home after your procedure, please tell your orthoptist.
How will my eye feel after the injection?
After your injection you may have one or more of the following side effects. These are all temporary and will get better by themselves.
Some patients have an ache in their eye for a while after their injection. If it is no better after 1 hour, take whatever medication you would normally take for a headache, for example paracetamol.
The direction of your squint may temporarily reverse. Your eye will gradually straighten as the effect wears off.
Temporary double vision; covering one eye can stop this. If this is significant and bothers you, do not drive until it wears off.
Temporary drooping of the eyelid on the side of the injection. This usually settles after a few weeks. To reduce this risk, avoid lying down and remain in an upright position for the rest of the day.
Slight bruising of the surface of the eye.
If you have any concerns about this risks, please speak to your orthoptist.
Will I need a follow-up appointment?
Most patients have a follow-up orthoptic appointment 1 week after their injection.
Will I need further injections?
If the injection does not work, it can be repeated the following month. If the injection works well, it may form part of long-term treatment and can be repeated at intervals.
Is there anything I should do once I return home?
We ask you to remain upright for as long as possible after your injection. Preferably into the late evening on the day of your injection. This helps stop the toxin leaking into the surrounding muscles.
Further information
For more information visit the Squint Clinic, or contact the Orthoptic Department on telephone 01227 868615.
Please note:
If you might be pregnant, please let us know.
If you have any reason to believe you might be a carrier of hepatitis or the HIV virus, please make sure that you tell the doctor who sees you in the Eye Clinic. The information is confidential, but it is essential that your doctor is told.
References
[Website last accessed 24th September 2025)
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