A lazy eye is a childhood condition that occurs when the vision in one eye does not develop properly.
This means that the child can see less clearly out of one eye and relies more on the 'good' eye.
The medical term for lazy eye is amblyopia.
A lazy eye is an uncommon but certainly not rare condition. It is estimated that 1 in 50 children will get one. Children are usually diagnosed with a lazy eye around the age of four.
How do I know if my child has a lazy eye?
Children with a lazy eye usually have problems accurately judging the distance between themselves and objects, which can make tasks such as catching a ball more difficult. In some cases you may notice that one eye looks different to the other (this could be due to a squint).
Younger children are often unaware that there is anything wrong with their vision and if they are, they are usually unable to explain what is wrong. Older children may complain that they can't see as well through one eye.
Read more about the symptoms of a lazy eye.
When to seek medical advice
Many cases of lazy eye are diagnosed during routine eye tests before parents realise that there is a problem. Children should have an eye test before they start school and then further tests at least every two years.
However, you should see your GP if you are concerned about your child's eyesight as they can refer your child for further testing by an eye specialist (ophthalmologist).
What causes a lazy eye?
The eyes work like a camera. An image made up of light comes through the lens of each eye and is beamed on to a light-sensitive layer of tissue called the retina.
The retina translates the image into nerve signals that are sent to the brain. The brain then combines the signals from each eye into a three-dimensional image.
A lazy eye occurs when the brain ignores one of the eyes and relies more heavily on the other. This can be due to a number of eye problems, including a squint (when the eyes don't look in the same direction) or a difference in the quality of vision between the eyes - for example, if one eye is short-sighted.
Left untreated this can lead to a permanent loss of vision in the affected eye.
Read more about the causes of a lazy eye.
Treating a lazy eye
The majority of cases of lazy eye can be treated, usually in two stages.
Firstly, the underlying problem is corrected, for example using glasses to correct a squint.
The child is then encouraged to use the affected eye again. This can be done with eye patches to cover the stronger eye or using eyedrops to temporarily impair the vision in the strong eye.
Treatment is effective, but it's a gradual process, taking many months to work.
Read more about treating a lazy eye.
Providing the condition is properly diagnosed and treated at an early age (ideally around two), then the outlook for children with a lazy eye is usually good.
The weaker eye will not normally return to perfect vision, but there is usually enough vision to avoid problems later in life.
It's more difficult to treat if the eyesight has finished developing (usually around the age of seven), although it is still possible to significantly improve the vision in the weaker eye.