Posterior capsule opacification: cloudy vision after cataract surgery

During cataract surgery the cloudy natural lens is removed and replaced with a clear artificial lens. The NHS explains that the surgeon makes a tiny opening through the clear layer at the front of the lens, which is called the lens capsule, and places the new lens inside the capsule, which holds it in place. The back part of the capsule, the posterior capsule, is left in position.

Torbay and South Devon NHS Foundation Trust describes the posterior capsule as a fine transparent membrane behind the natural lens which is left to support the lens implant. With time this membrane may thicken and mist over, causing a gradual reduction of vision. This is known as capsule opacification. Moorfields adds that thickening means light is less able to travel through to the retina, the light-sensitive layer at the back of the eye.

It is not a return of the cataract and it is not a sign that the operation failed. It is a change in the membrane that was deliberately left behind. That is why the treatment is a simple laser opening rather than another operation.

Moorfields says that sight can become cloudy or blurred, or you may have problems with bright lights and glare. The NHS cataract surgery page says that sometimes vision can become cloudy months or years after surgery, and that this may be a condition called posterior capsule opacification.

The NHS advises going to an optician if your vision gets cloudy or blurry, you find it hard to focus, your eye becomes red or painful, you see light or dark areas in your vision, or it becomes uncomfortable or painful to look at bright light. Because other eye conditions can look similar, the optician or eye clinic will check that PCO is the cause before arranging treatment.

Some changes in the eye are not PCO and need prompt assessment. The NHS says to get help from NHS 111 if floaters (dots and lines) suddenly appear or suddenly increase in number, you get flashes of light, you have a dark curtain or shadow moving across your vision, or your vision gets suddenly blurred. It states that these could be signs of a detached retina.

The Moorfields leaflet gives similar advice after laser treatment: contact the clinic for pain not relieved by your normal painkillers, noticeable redness, worsening sight, or flashing lights or a shadow or curtain in the vision, and use an emergency eye service or A&E if needed.

The treatment is a YAG laser capsulotomy. Torbay and South Devon describes it as an outpatient procedure in the eye clinic: your vision is checked, drops are used to dilate the pupil and blur the vision for several hours, an anaesthetic drop is put in, and a contact lens is placed on the eye to focus the laser beam. The procedure lasts approximately 5 to 10 minutes, during which you hear beeping noises and see bright lights, and you should not feel any pain.

Moorfields explains that the laser cuts a hole in the opaque membrane behind the implant, which allows light to reach the retina again. It says that for the vast majority of people vision improves, that it may take several days before vision is fully restored, and that because there are no incisions or stitches you can normally return to daily activities straight away. It advises expecting to be in hospital for up to two hours because of the checks and dilating drops.

You should not drive yourself home after the drops. Torbay says you may resume driving the following day and may visit your optician a week after treatment to check whether your glasses need changing.

Both NHS eye units describe the laser as very safe. Moorfields lists common effects: a brief rise in eye pressure (checked, and treated with drops or a tablet if needed), uncommon inflammation inside the eye that responds rapidly to anti-inflammatory drops, and floaters, which it describes as harmless clumps of cells. Rarely, it says, the laser can cause a retinal detachment, which can happen days, weeks or months afterwards and is more likely if you are very short-sighted. It adds that retinal detachment surgery is normally very successful in preserving or restoring good vision, and that minor scratches to the lens implant are occasionally unavoidable but very rarely cause visual problems.

Torbay and South Devon lists a small risk, less than 2 per cent, of retinal tear or detachment, swelling of the retina (macular oedema) causing blurring that can take several weeks to improve, and worsening of glaucoma which can usually be treated with eye drops. It says some floaters are normal and tend to settle within a few weeks.

On the NHS, PCO is usually identified by the optician or the eye clinic and treated in the ophthalmology outpatient department. The Moorfields leaflet notes that patients have the right under the NHS constitution to begin consultant-led treatment within 18 weeks of GP referral.

Laser capsulotomy is also offered by private ophthalmology providers, often as a quicker appointment. The procedure and its risks are the same, so it is reasonable to ask the provider how they check the retina beforehand and who to contact if symptoms change afterwards.