What is amblyopia?

A lazy eye, also known as amblyopia, is a childhood condition that occurs when the vision in one eye does not develop properly. It is the most common eye disease in children occurring in about 1 in 50 children, due to the suppression of visual information passed between the eye and brain.

For children up to seven years of age it can normally be treated by patching the good eye and forcing the amblyopic eye to see. Much research is being done into the optimum time for patching and the difficulties involved.

Causes of 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 ignores one of the eyes and relies more heavily on the other. This means that the child can see less clearly out of one eye and relies more on the ‘good’ eye. 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 and the other is long-sighted.

Left untreated, this can lead to a permanent loss of vision in the affected eye.

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.

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 are usually diagnosed with the condition around the age of three or four.

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).

Treatment for a lazy eye

The majority of cases of lazy eye can be treated, usually in two stages.

First, 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.

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 six), although it is still possible to significantly improve the vision in the weaker eye.

Find out how Assistive Technology helps to manage tasks made difficult by low vision and blindness.