Cataracts occur when changes in the lens of the eye cause it to become less transparent (clear). This results in cloudy or misty vision.
The lens is the transparent structure located just behind the pupil (the black circle in the centre of the eye).
It allows light to pass through to the light-sensitive layer of tissue at the back of the eye (retina).
Cataracts most commonly affect older adults (age-related cataracts), but some babies are born with cataracts.
Children can also develop them at a young age. These are known as childhood cataracts.
Childhood cataracts are often referred to as:
Cataracts in babies and children are rare. It's estimated they affect between 3 and 4 in every 10,000 children in the UK.
In children, cataracts can affect 1 or both eyes.
Cloudy patches in the lens can sometimes get bigger and more can develop, resulting in the child's vision becoming increasingly affected.
As well as poor vision, cataracts can also cause "wobbling eyes" and a squint, where the eyes point in different directions.
When your child is very young, it can be difficult to spot signs of cataracts.
But your baby's eyes will be routinely examined within 72 hours of birth and again when they're 6 to 8 weeks old.
Sometimes cataracts can develop in children after these screening tests.
It's particularly important to spot cataracts in children quickly because early treatment can reduce the risk of long-term vision problems.
You should visit your GP or tell your health visitor if you have any concerns about your child's eyesight.
There are a number of reasons why a child may be born with cataracts or develop them while they're still young.
But in many cases it isn't possible to determine the exact cause.
Possible causes include:
Read more about the causes of childhood cataracts.
Cataracts in children are often not too bad and have little or no effect on their vision.
But if cataracts are affecting your child's vision, they can slow down or stop their normal sight development.
In these cases, surgery to remove the affected lens (or lenses) will usually be recommended as soon as possible.
Replacing the focusing power of the lens is as important as the surgery to remove it.
The affected lens may sometimes be replaced with an artificial lens during surgery, although it's more common for the child to wear contact lenses or glasses after surgery to compensate for the lens that was removed.
It can be difficult to predict exactly how much better your child's vision will be after treatment, although it's likely there will always be a degree of reduced vision in the affected eye (or eyes).
But many children with childhood cataracts are able to live a full and normal life.
Read more about treating childhood cataracts.
Cataract surgery is generally successful, with a low risk of serious complications.
The most common risk associated with cataract surgery is a condition that can affect artificial lens implants called posterior capsule opacification (PCO), which causes cloudy vision to return.
Another important risk of surgery is glaucoma, where pressure builds inside the eye.
Without successful treatment, glaucoma can cause irreversible damage to key structures in the eye.
Although some of the possible complications of cataract surgery can affect your child's vision, they can often be treated with medication or further surgery.
Read more about the complications of childhood cataracts.
It's not usually possible to prevent cataracts, particularly those that are inherited (run in the family).
But following the advice of your midwife or GP to avoid infections during pregnancy (including making sure all your vaccinations are up-to-date before getting pregnant) may reduce the chances of your child being born with cataracts.
If you previously had a baby with childhood cataracts and are planning another pregnancy, you may wish to speak with your GP about whether genetic counselling would be appropriate.
Genetic counselling can help couples who may be at risk of passing an inherited condition on to their child.
If your child has had cataracts, your clinical team will pass information about him or her on to the National Congenital Anomaly and Rare Diseases Registration Service (NCARDRS).
This helps scientists look for better ways to prevent and treat this condition. You can opt out of the register at any time.