A 'lazy eye' is a childhood condition where the vision does not develop properly. It's known medically as amblyopia.
It happens because one or both eyes are unable to build a strong link to the brain. It usually only affects one eye, and means that the child can see less clearly out of the affected eye and relies more on the 'good' eye.
It's estimated that 1 in 50 children develop a lazy eye.
How to tell if your child has a lazy eye
A lazy eye does not usually cause symptoms. Younger children are often unaware that there's anything wrong with their vision and, if they are, they're usually unable to explain what's wrong.
Older children may complain that they cannot see as well through one eye and have problems with reading, writing and drawing.
In some cases, you may notice that one eye looks different from the other. However, this is usually a sign of another condition that could lead to a lazy eye, such as:
If your child is too young to tell you how good their vision is, you can check their eyes by covering each eye with your hand, one at a time.
They might object to covering the good eye, but they might not mind if you cover the lazy eye.
If they try to push your hand away from one eye but not the other, it may be a sign they can see better out of one eye.
When to get medical advice
Lazy eye is often diagnosed during routine eye tests before parents realise there's a problem.
If you want to be reassured about your child's vision, they can have their eyes tested when they're old enough to attend a sight test at a high-street opticians, which is usually after they're 3 years old.
All newborn babies in the UK have an eye test in the first days of life, and then again at 2 to 3 months old, to look for eyesight problems such as cataracts.
Problems like squint and short or long sight may not develop until the child is a few years old.
It's difficult to treat lazy eye