Cataract surgery is very common and the associated risks are very low, but can be serious.
The Royal National Institute of Blind and Partially Sighted People (RNIB) estimates that less than 2% of people experience any serious complications that require further surgery.
However, ask your eye surgeon ( ophthalmologist) to explain the possible risks before your operation. If a severe cataract is not treated, it is possible loss of sight may be permanent.
The most common risk associated with cataract surgery is developing a condition called posterior capsule opacification (PCO). This is where part of the lens capsule (the 'pocket' that the lens sits inside) thickens and causes cloudy vision. This is not the cataract returning, but cells growing over the back of the artificial lens.
PCO is common, affecting the vision of up to half of everyone who has cataract surgery. PCO usually develops between six months and five years after the operation.
If you develop PCO, you may need another operation to correct it using laser eye surgery (when energy beams are used to cut through part of the eye). During laser eye surgery, the cloudy part of the lens capsule will be removed, with enough of the lens being left to hold the artificial lens in place.
The procedure should only take around 15 minutes, and your vision should either be improved immediately or within a few days. As no surgical incisions or stitches are necessary, you should be able to return to your normal activities straight away.
Other possible complications of cataract surgery are much rarer but can include:
- infection in the eye
- bleeding in the eye
- inflammation ( swelling and redness) in the eye
- tearing of the lens capsule
- a bit of the cataract dropping into the back of the eye
- damage to other parts of the eye, such as the cornea (the transparent outer layer of the eye)
- retinal detachment
- inability to remove all of the cataract
You should seek immediate medical attention if you experience sudden loss of sight or increasing pain after cataract surgery.
However, the College of Optometrists has estimated that, in most cases, the risk of complications occurring during cataract surgery is less than 1 in 100. Although tearing of the lens capsule may occur more frequently than this.
It is usually possible to successfully treat complications that arise from cataract surgery. Occasionally, your vision may be worse than it was before surgery or there may be permanent damage to your eye, causing a loss of sight. However, this is rare.
Cystoid macular oedema
One possible complication that can cause loss of vision is cystoid macular oedema. This is where fluid builds up between layers of the retina (the layer of nerve cells that lines the inside of the back of the eye).
There are two different types of cystoid macular oedema:
- angiographic cystoid macular oedema
- clinical cystoid macular oedema
Angiographic cystoid macular oedema is very common, but does not affect vision. Clinical cystoid macular oedema can cause vision loss and is thought to make up between 0.1% and 12% of cases.
Cystoid macular oedema may be treated with non-steroidal anti-inflammatory drugs (NSAIDs), although research into other treatments is continuing.
Childhood cataract surgery
More risks are involved with childhood cataract surgery. They include:
- glaucoma (increased pressure inside the eye that affects vision)
- squint (strabismus), where one eye turns inwards, outwards, upwards or downwards while the other eye looks forwards
- abnormalities that affect the pupil (the black circle at the centre of each eye)
- vision becoming cloudy again (visual axis opacification or posterior capsule opacification (PCO))
- retinal detachment, when the retina (the layer of nerve cells inside the back of the eye) becomes separated from the inner wall of the eye
- infection, such as endophthalmitis (a rare bacterial infection)
If childhood cataracts are not treated, the child may become blind. Even if the cataracts are removed, visual impairment or blindness can remain.
The natural lens in your eye can change shape. This is how it enables your eye to focus on objects both near to you and further away.
Fixed strength (monofocal) and multifocal replacement plastic lenses cannot do this. Therefore, after cataract surgery, you may also need reading glasses or glasses for distance vision.
One review of a number of studies found that 95% of people with a monofocal lens and 68% of people with a multifocal lens needed glasses after having cataract surgery.
Another type of artificial lens, called an accommodating lens, aims to allow the eye to focus on both near and distant objects.
The National Institute of Health and Clinical Excellence (NICE) has reported some evidence that this type of lens improves clearness of vision. However, more evidence is needed to confirm this lens improves accommodation (how the lens adapts to focus images). NICE also noted this area of technology is changing rapidly, and it is not yet fully understood how these lenses work.
Read the NICE guidance on the use of accommodating replacement plastic lenses and multifocal lenses.