Cataracts - laser treatment following cataract surgery

Sometimes, following cataract surgery 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.

Why laser treatment is sometimes needed following cataract surgery


This complication is called posterior lens capsule opacification or PCO.

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

How the eye works

When you look at something, light passes through the front of your eye where it is focused by the cornea and then the lens, onto the retina at the back of your eye. The lens is normally clear so that light can pass directly through it to focus on your retina. The lens is clear because of the way that its cells are arranged.

The lens focuses light onto the retina, which converts this light into electrical signals. A network of nerves delivers these signals from the different parts of the retina to the optic nerve and then on to the brain. The brain interprets these signals to 'see' the world around you.

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 the operation 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 surgery?

Occasionally following a cataract operation, usually one to two years after the operation but sometimes earlier or later than this, 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. Some people say it is like their cataract has come back.

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 PCO. 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.

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.

Is the laser treatment painful?

The procedure is quick and painless. It is usually done in an outpatient clinic and normally takes about 15 minutes. The actual laser part of the procedure may only take five minutes.

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. 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. If no contact lens is used you may not need to have the anaesthetic.

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 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 as the laser works.

What happens after laser treatment?

Most people notice it can take a few days for their sight to become clear again. Occasionally following the laser treatment you may notice some floaters. Floaters are harmless little clumps of cells which move around inside the vitreous (the jelly which fills the inside of the eye). You may see them as dots, circles, lines, clouds or cobwebs.

You may notice floaters after your laser treatment as it can take a few days for the part of your lens capsule which was cut away to settle on the bottom of your eye. For some people floaters can last for a few weeks following treatment, but with time for most people, they will become less obvious as your brain learns to ignore them.

Because the laser treatment doesn't require any incisions (cuts) or stitches, you are normally able to return to your daily activities straight away. There is also no risk of introducing an infection inside the eye.

You should not drive yourself home after the treatment as it can take some time for the drop that dilates your pupil to wear off and vision may still be blurry for one or two hours following the laser. There is no reason why you should not be driven, take a cab or use public transport if you feel up to it. Most people do not usually require any drops or medication following treatment.

Are there any risks?

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

For some people laser treatment for PCO can cause eye pressure to rise. This can be a worry if you already have a condition called 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, and if it is found to be high, may give you 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. You can tell a retinal detachment may be happening because you tend to get a new batch of floaters, flashing lights or a curtain coming over and obscuring your vision. You should see your doctor at the hospital urgently if this happens.

It is important to remember that these problems are extremely rare complications of this treatment and the vast majority of people get an excellent improvement in their vision following laser experiencing no problems.

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 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.


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

105 Judd Street

The RNIB Helpline can:

  • 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, Monday to Friday 8.45am to 5.30pm.

We're here to help


Contact Us