Glaucoma is the name for a group of eye conditions which cause damage to the optic nerve at the back of the eye. If the natural fluid which fills the eye cannot drain away properly, this can result in a build-up of pressure within the eye. The high pressure can cause loss of vision and, if very high, pain or discomfort. To lower the eye pressure, a surgical procedure known as a trabeculectomy can be carried out.


A small opening is made in the white part of the eye near the upper eyelid to form a drainage channel. The opening allows the eye fluid to drain away into a reservoir known as a filtering bleb and hence reduces the eye pressure. The bleb is formed during surgery from the normal covering of the eye. The bleb will have the appearance of a blister-like bump on the white of the eye, usually under the upper eyelid. An anti-scarring drug may be used to improve the success of the operation.

Why do I need this procedure?

There are many reasons why your eye specialist (ophthalmologist) might recommend a trabeculectomy

  • The eye pressure is not being controlled adequately with your current medication
  • The glaucoma is worsening
  • Problems with your glaucoma medication

What is the success rate of the operation?

About 90% of trabeculectomies go well. The intraocular pressure (IOP) will be lowered to your surgeon’s preferred level. After a successful trabeculectomy, it may be possible to reduce glaucoma eye drops. If the trabeculectomy is not successful the operation may need to be repeated or further treatment may be required. The aim of the operation is to reduce the risk of further damage to the optic nerve. It will not improve sight, but will hopefully help protect vision in the longer term.

What are the risks?

Some risks involved are:

  • Bleeding
  • Infection
  • Inflammation
  • For a period of time IOP may become too high or too low.
  • In some cases a cataract may develop. This can be treated by an operation if necessary.
  • Serious complications are rare, but occasionally the sight can get worse after the trabeculectomy and not recover.

Before the operation

  • If you are taking warfarin or aspirin tablets, please discuss the dose with your ophthalmologist
  • Please take all other medication as normal or as instructed. Your ophthalmologist will advise you on which eye drops.
  • You will need to fast on the day of the operation.

During the operation

A trabeculectomy can take up to an hour and can be carried out under local or general anaesthetic. The ophthalmologist will discuss which option is most suited to you.Please expect to be at the hospital/clinic for up to 4 hours.

After the operation

  • Your sight will often be blurred immediately after the operation. This will usually improve after a week or two, but can last up 6 weeks.
  • Your eye will be watery for a short period of time.
  • You may have a gritty sensation in the eye for a week or two.
  • Mild pain can be relieved by taking products such as paracetamol.
  • You will be given new eye drops to reduce scarring at the operation site. These usually need to be taken every hour initially but the frequency will be explained to you by your ophthalmologist. If you are on more than one eye drop, wait five minutes between applications of the different eye drops. You must follow the detailed instructions given to you.
  • You will be seen regularly to monitor your eye’s recovery.
  • In some cases you may require an injection to prevent scar tissue forming which can block the drainage channel.
  • The stitches may also need to be adjusted or removed.
  • Following the operation you should rest and take things easy but will be able to carry out normal day to day activities.
  • Wear sun glasses if the light is too bright for comfort. If you wear contact lenses you should discuss this with your ophthalmologist. If you wear glasses your prescription may need to be changed following surgery; your ophthalmologist will advise you.
  • You should not rub your eye, undertake strenuous exercise or heavy gardening and avoid coughing and sneezing if possible.
  • Your ophthalmologist will advise you when you will be able to drive and return to regular work.


If you experience severe pain, sudden loss of vision or discharge contact your ophthalmologist or the eye hospital or clinic where your surgery was performed.


Download the fact sheet here.