Posterior capsule opacification - why laser treatment is sometimes needed following cataract surgery

Posterior capsule opacification (PCO) is a fairly common complication of cataract surgery. Sometimes you can develop a thickening of the back (posterior) of the lens capsule which holds your artificial lens in place.

This thickening of the capsule causes your vision to become cloudy. If this happens you may need to have laser treatment to make vision clear again. Once you have had the laser treatment for PCO it doesn’t normally cause any long term problem with your sight.

Why is laser treatment sometimes needed following cataract surgery?

There is a risk of developing posterior lens capsule opacification (PCO) following your cataract surgery. PCO is a complication that causes the back of the lens capsule (which holds your artificial lens in place) to thicken which causes cloudy vision. If this happens you may need to have laser treatment to make vision clear again.

Posterior lens capsule opacification is fairly common and once it has been treated does not normally cause any long term problems with your sight.

The procedure to treat posterior lens capsule opacification (PCO) is a painless process which is usually done in an outpatient clinic, and normally takes about 15 minutes.

Cataract surgery 

What happens during cataract surgery?

A cataract is a clouding of the lens in your eye and normally occurs as part of the ageing process. When you develop a cataract, light is unable to pass directly through your lens to the retina, resulting in blurred vision.

Cataracts are removed by surgery. During cataract surgery the natural lens of your eye is replaced by an artificial lens. This new artificial lens is placed in your lens capsule, the membrane which held your natural lens. Your lens capsule is clear and remains clear following your cataract surgery.

What happens after cataract surgery? 

Occasionally following cataract surgery you may start to have difficulties with your vision again.

This is not a re-growth of your cataract, but is due to the thickening of the back of the lens capsule. This is called posterior lens capsule opacification, sometimes shortened to 'PCO'.

PCO happens because more cells grow over the back of the capsule causing it to thicken. Thickening of the capsule means that light is less able to travel through to the retina at the back of your eye. Sight can become blurred or you may have problems with bright lights and glare. PCO causes problems with your sight which are very similar to the changes you may have had when your cataract first started to cause you problems. 

There are some reasons why you may be more likely to develop PCO. The younger you are when you have cataract surgery, the more likely it is that this thickening will occur. PCO is also more common in some unusual situations, such as where inflammation (swelling) is present in your eye or if someone has the eye condition retinitis pigmentosa.

Research shows that an artificial lens which has a square, rather than rounded edge can decrease the chances of someone developing posterior lens capsule opacification . This is because a square edge on the lens seems to make it more difficult for cells to grow across the back of your capsule. Most lenses are now manufactured with a square edge to reduce the risk of PCO.

What can be done about posterior lens capsule opacification? 

Usually, PCO can be treated quite simply. Using a laser, a doctor can make a hole in part of the back of your lens capsule so that the light can once again pass directly to the retina. For the vast majority of people this can improve vision. This procedure is called Nd:YAG laser capsulotomy. Nd:YAG is the type of laser used for this treatment. Sometimes this laser is also referred to as just 'YAG'.

How does the laser work? 

Lasers are beams of energy which can be targeted very accurately. The Nd:YAG laser uses very low energy levels and can delicately cut the lens capsule without any risk of damage to other parts of your eye.

What are the risks of laser treatment? 

The laser procedure is considered very safe. Though there are some risks, serious side effects are very rare. If a contact lens is used your eye may be a little sore following the treatment, but this should soon wear off.

For some people laser treatment for PCO can cause eye pressure to rise. This can be an issue if you already have a pre-existing eye condition such as glaucoma, as your eye pressure may already be higher than normal. If your doctor is concerned about this they will check your eye pressure soon after the laser treatment. If your eye pressure has increased, you  will be provided with some eye drops or a tablet to bring it back down.

Rarely, laser can cause a retinal detachment which can happen days, weeks or months after the treatment. This is more likely to happen if you are very short-sighted. It is important to stress that these risks are extremely rare complications of the laser treatment. The vast majority of people get an excellent improvement in their vision following laser without experiencing any issues.

What happens during laser treatment? 

Sometimes, but not always, the doctor may use a contact lens to help to keep your eye in the right position. If the doctor decides this is necessary then they will also use a drop to anaesthetise (numb) the front of your eye so that you do not feel any discomfort.

In most cases the doctor will use an eye drop to dilate (widen) your pupil before the treatment. This can make your vision more blurry.  Once your pupil is dilated, you will be asked to place your head on the headrest of the laser machine. This will help to keep your head and eye still while the doctor uses the laser to remove part of the capsule.

The doctor focuses the laser exactly onto the back of the lens capsule in order to cut away a small circle shaped area. This leaves some of the capsule to keep your artificial lens in place (like a cuff around the lens) but removes enough in the middle to allow the light to pass directly through to the retina. 

The very small part of your lens capsule which is cut away falls harmlessly to the bottom of the inside of your eye where it eventually breaks down. The laser uses a wavelength of light that cannot be seen, but you may notice a red light which helps the doctor focus the laser beam. Each laser pulse is over in a fraction of a second and you should not feel any pain or discomfort. You may notice a few flashing lights or hear some faint clicks coming from the machine as the laser works.

What happens after laser treatment? 

It may take a few days for your sight to become clear again, and you may notice 'floaters' after your laser treatment. Floaters are harmless clumps of cells which move around inside the vitreous (a jelly-like substance which fills the inside of the eye). You may see floaters as dots, circles, lines, clouds or cobwebs.

Because the laser treatment does not require any incisions or stitches, you are normally able to return to your daily activities straight away.  

Alert your doctor immediately if you experience any of the following:

  • new batch of floaters,
  • flashing lights, and/or a dark curtain moving up, down or across your vision

as these may be a sign that you are experiencing retinal detachment.

You should not drive yourself home after the treatment as it can take some time for the drops that dilate your pupils to wear off, and your vision may still be blurry following the laser. Please ensure that you arrange for alternative transportation.

What about my sight?

After this treatment your sight should be restored to the level you had following your original cataract surgery, provided no other problems have developed in your eye. You will still have to use any glasses as before, but your vision should be clear again with these, unless you have any other eye conditions affecting your sight.


Being diagnosed with an eye condition, like cataracts, can be upsetting. You may find that you are worried about the future and how you will manage with a change in your vision. All these feelings are natural.

Some people may want to talk over some of these feelings with someone outside their circle of friends or family. RNIB can help, with our telephone Helpline and our emotional support service. Your GP or social worker may also be able to help you find a counsellor if you think this would help you.

Help to see things better 

PCO can cause your vision to become blurry and you may have glare or difficulties in bright light before you have the laser treatment. You may also find reading difficult. There are a lot of things you can do to make the most of your vision if you are having any difficulties. This may mean making things bigger, using brighter lighting, or using colour to make things easier to see.

Our Helpline can also give you information about the low vision services available, schooling, work and employment and our website offers lots of practical information about adapting to changes in your vision and products that make everyday tasks easier.

Contact us

The RNIB Helpline can:

  • put you in touch with an RNIB specialist advice service such as welfare benefits and rights, education, employment, legal rights, emotional support, daily living help and residential care
  • send you free information and leaflets
  • give you details of support groups and services in your area.

Call us on 0303 123 9999 or email [email protected], Monday to Friday 8am to 8pm and Saturday 9am to 1pm.

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