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Posterior Capsule Opacity

What is a Posterior Capsule Opacity (PCO)?

Cataract surgery removes a cataract (cloudy lens) from its cellophane-like lining called the lens capsule. An artificial lens (IOL) is then inserted into the capsule to replace the natural lens. Weeks to years after cataract surgery, the capsule may become cloudy or wrinkled and cause blurred vision. This is called a posterior capsule opacity (PCO). It’s also sometimes referred to as a “secondary cataract” or “scar tissue.”


  • Clouded, blurred or dim vision (may feel like the cataract has returned)

  • Increasing difficulty with night vision

  • Sensitivity to light and glare

  • Need for brighter light

  • Increased difficulty with reading or near tasks

Cause of PCO:

As stated above, during cataract surgery the natural lens of the eye is replaced by an artificial lens. This IOL is placed inside the lens capsule. This lens capsule is generally clear at this time. PCO occurs because cells remaining after cataract surgery grow over the back surface of the capsule causing it to thicken and become slightly opaque. Less light is able to travel through to the retina at the back of the eye causing blurred vision. PCO can affect both eyes, but each eye may be affected at different times.


PCO is treated by a very low risk, quick, painless laser treatment. It is an outpatient procedure. With posterior capsulotomy (often referred to as YAG), a laser is used to make an opening in the cloudy capsule. This allows light to pass through again for clear vision.

At the appointment your eyes will be dilated to widen the pupil for a better view of the PCO. Once your pupil is dilated, you will be asked to place you head of the headrest of the laser machine. A laser is then focused 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 the IOL in place but removes enough in the middle to allow the light to pass through. You may notice a few flashing lights or hear some faint clicking noises coming from the machine as the laser works. The procedure generally takes no more than 5-10 minutes.

After the procedure, usually you can do all of your normal daily activities. As long as there are no other problems affecting your vision, your sight should improve within 24 hours. You will still have to use any glasses you used before the PCO developed. Some people will notice new “floaters” after treatment. These are harmless clumps of cells moving around inside the vitreous gel inside the eye. These will settle down and become less noticeable with time.

You will generally only need to have laser treatment for PCO once. In very rare instances, cells may develop again in the area of the posterior capsule, or the opening in the capsule can shrink. If this does happen, it is possible to repeat the laser treatment if needed.

Risks of Laser Treatment:

Serious side effects from laser treatment for PCO are very rare. However, as with any surgery, there are possible risks and complications.

Retinal Detachment

Rarely, laser can cause a retinal detachment which can happen days, weeks or months after the treatment. The following symptoms may be a sign that you have developed this: increase in floaters, flashing lights and/or a dark curtain over your vision.

Increased Intraocular Pressure

More common if already diagnosed with a pre-existing condition such as glaucoma. After the procedure, your eye pressure will be checked.

Dislocation of the IOL through the posterior capsule opening

Inflammation in the eye, possible requiring treatment with steroid eye drops


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