Pre-operative Assessment

This procedure will only be carried out with your consent and you will be asked to sign a consent form when you are put on the waiting list.

You will have a preoperative assessment to determine if you are suitable for the procedure and if any further investigations will be required.

To reduce the risk of bleeding during the operation we usually ask you to stop medicines like aspirin, clopidogrel or warfarin. It is important to talk to us first though, to make sure it is safe to stop taking any tablets. Don’t just stop taking them!

How is the operation done?

In most circumstances you will have the operation performed under a local anaesthetic, which means you will be awake during the surgery. You will be asked to keep your eye still and lie as flat as possible.

Before the operation you will have a small injection around the eye which will make the eye numb and will also prevent the eye moving and may blank out the vision during the operation.

If you are very anxious or cannot keep still, and your general health is good, then you could have sedation or even a general anaesthetic, which involves you being asleep throughout the operation.

After anaesthesia has been given, one end of the PRESERFLO MicroShunt tube is inserted into the eye space in front of the iris, called the anterior chamber. The rest of the tube is tucked away under the protective membrane ( Conjunctiva ) that surrounds the eye.

This creates a small escape tunnel allowing the fluid to drain away into the space under the protective membrane, to form a filtering bleb. The protective membrane is then securely closed with small sutures.

During the procedure, a special medication (mitomycin) is applied around the incision site to reduce scarring and ensure the channel does not close after the surgery.

After a few weeks a small blister forms at the site of surgery called a bleb, which remains on the eye beneath the upper eyelid (so you can’t normally see it).

The bleb collects the aqueous from inside of the eye in a controlled way and lets it absorb into the circulation. This lowers the pressure in the eye.

Benefits of Preserflo Microshunt

To prevent visual loss by lowering the pressure in the eye


Possible complications from the surgery

These might mean that the operation doesn’t work properly and we might have to give you drops or do other operations to try to fix it.

Problems with the operation

Inflammation and scarring can stop the fluid draining out, which makes the pressure go up and you may need drops, injections or surgery.

The wound can leak, which gives a very low pressure and you may need surgery to seal it up.

Other problems

  • Complete loss of vision is very rare and is seen in less than 1:2000 patients
  • Infection is rare, but is an emergency if it happens
  • Bleeding inside the eye: the risk is higher if you are taking blood thinning medicines e.g. aspirin, warfarin or clopidogrel.
  • Cataract: if you already have an early cataract this operation might make it worse so you would need cataract surgery. If it is a problem the doctor will discuss it with you after the operation.
  • Droopy eyelid and double vision may get better on their own or you may need special glasses or surgery.
  • Retinal detachment (which can lead to sight loss)
  • Allergy to the postoperative medications

How long will I be in hospital?

In most cases the operation will be performed as a day case .

You should have a responsible adult to come with you, as an escort.

If you are fit to travel, you may come in on public transport or taxi, otherwise arrangements will have to be made for hospital transport if you do not fall into this category.

If your operation is in the morning then you can have a light breakfast, if it is in the afternoon you may have a light lunch. If you are a diabetic patient have your normal diabetic diet.

Take all your medications as normal unless instructed otherwise.

After the operation you will be able to go home within a few hours.

After the operation

Immediately after the procedure, the nursing staff will explain to you all the precautions and the drops you should use. They will go through with you detail the do’s and don’ts after the operation.

In most cases, an eye pad and plastic shield will be placed over your eye after surgery. The next day you can remove this dressing and put in your drops as instructed.

Pain is unusual after this operation but the eye may feel tender. A mild pain reliever like paracetamol is usually enough to make it feel better. Sudden, severe or deep-seated pain should be reported immediately using the numbers provided.

Do not be alarmed if the vision in the eye is worse than it was before the operation, this is normal. It can take a few weeks before the vision is the same as it was before. You will not notice an improvement in your vision after this operation. The aim of the procedure is to prevent reduction in vision due to glaucoma.

Stop Glaucoma drops to the eye which has been operated on but continue to use those prescribed to the other eye.

After surgery Avoid

  • Lifting heavy objects
  • Vigorous head shaking
  • Rubbing the eye
  • Using eye make-up
  • Swimming
  • Driving until after your first outpatient appointment when this can be discussed with the doctor.

Ensure you


  • Wash your hands before putting in your drops
  • Wear the eye shield provided overnight for at least two weeks after surgery
  • Continue to use eye drops as instructed and if you run out of eye drops get a repeat prescription from your GP surgery.
  • When bending down do so slowly and try to keep your head in the upright position
  • Wear sunglasses to make the eyes more comfortable in bright light



  • Read
  • Watch T.V.
  • Go for walks
  • Cook


Will the operation improve my sight?

Unfortunately the operation cannot bring back any sight that has already been lost. After the operation your sight may be blurred and seem worse but this is only temporary. Your eye will need time to heal.

How often will I be seen in clinic after the operation?

To ensure that all is going well you will need to be seen regularly in the eye clinic. Visits will tend to be as follows:

  • The day following the operation
  • A week after the operation
  • Then every two weeks for approximately six weeks
  • Monthly for three months