A lazy eye, also known as amblyopia, is a childhood condition that occurs when the vision in an eye does not develop properly. 

This usually means that the child can see less clearly out of one eye and relies more on the "good" eye.

An estimated 1 in 50 children will develop a lazy eye and children are usually diagnosed with the condition around the age of four.

How do I know if my child has a lazy eye?

A lazy eye does not usually cause symptoms. 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.

In some cases you may notice that one eye looks different to the other. However, this is usually a sign of another condition that could lead to a lazy eye, such as a squint (when the eyes don't look in the same direction).

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 a vision test between the ages of four and five.

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 (opthalmologist).

Read more about diagnosing a lazy eye and vision tests in children.

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 onto 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 connections responsible for vision are not made properly. This can be because of:

• a reduction in the amount of light entering the eye
• a lack of focus in the eye
• confusion between the eyes – where the two images are not the same (such as a squint)

Left untreated, this can lead to the central vision of the eye never reaching normal levels.

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.

The underlying problem is first corrected. This can be done using glasses to correct the focus of the eye, which often helps to correct a squint as well.

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 eye drops to temporarily impair the vision in the strong eye.

Treatment is often effective, but it's a gradual process, taking many months to work.

Read more about treating a lazy eye.