A lazy eye (amblyopia) is a childhood condition where the vision in one eye doesn't develop properly.
This usually means that the child can see less clearly out of the affected eye and relies more on the "good" eye.
Anestimated 1in 30 to 1 in 50 children will develop a lazy eye.The condition is usually diagnosed around the age of four.
Lazy eye can sometimes affect both eyes, although this is rare.
A lazy eye doesn't 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 can't see as well through one eye andhave problems with reading, writing and drawing.
In some cases, you may notice that one eye looks differentfrom the other.
However,this is usually a sign of another conditionthat could lead to a lazy eye, such as:
One way to check your child'seyes is to cover 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.
Lazy eye is often diagnosed duringroutine eye tests before parents realise there's a problem.
Children should have their eyes testedonce they're old enough to attend a sight test, which is usually after they are 3.5 years old.
It's difficult to treat lazy eye after the age of 4.5, so it's a good idea for children to have an eye test between the ages of 3.5 and 4.5.
However, visit your GP if you have any concerns about your child's eyesight. If necessary, they can referyour child to an eye specialist (ophthalmologist) for further testing.
Light passes through the lens of each eye and reaches a light-sensitive layer of tissue at the back of the eye called the retina.
The retina translates the image into nerve signals that are sent to the brain. The brain combines the signals from each eye into a three-dimensional image.
A lazy eye occurs when the brain connections responsible for vision aren't made properly.
This can be the result of:
Left untreated, this canlead to the eye's central vision never reaching normal levels.
This can be done using an eye patch to cover the stronger eye, or eye drops to temporarily impair the vision in the stronger eye.
Treatment is often effective, but it's a gradual process that takes many months to work.
Find out what a lazy eye (amblyopia) is, what causes it and how it's diagnosed and treated.
Find out how a child's vision develops and how lazy eye is caused when something, such as a squint or refractive error, disrupts normal development.
Read about the routine eye tests that your baby will have and at what ages. It's important for a lazy eye (amblyopia) to be diagnosed and treated as early as possible.