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's not possible to determine the exact cause.
Some of the main causes of childhood cataracts are described below.
Cataracts present from birth (congenital cataracts) are sometimes caused by a faulty gene being passed to a child from their parents.
This fault means that the lens doesn't develop properly.
It's estimated there's a family history of congenital cataracts in around 1 in every 5 cases of the condition.
Recent research suggests genetic causes are responsible for the majority of bilateral congenital cataracts in the UK.
Cataracts can also be associated with conditions caused by chromosome abnormalities, such as Down's syndrome.
Chromosomes are the parts of the body's cells that carry the genes.
Congenital cataracts can also be caused by infections caught by the mother during pregnancy.
The main infections linked to an increased risk of congenital cataracts include:
Cataracts that develop in children after they're born are known as acquired, infantile or juvenile cataracts.
Causes of this type of cataracts can include:
But most of these problems are either rare or don't usually cause cataracts to develop in children.