Lazy eye (amblyopia)

Lazy eye occurs when a child's vision does not develop properly. The medical term for lazy eye is amblyopia.

Lazy eye typically happens when an underlying eyesight problem affects the images sent from the eye to the brain. This interrupts the normal development of a child's vision.

It often doesn't cause symptoms, especially in very young children, but can be detected with routine childhood eye tests. Once diagnosed, the weaker eye can be treated effectively if the underlying cause is identified and managed.

What is a lazy eye?

Lazy eye, which is known medically as amblyopia, happens when something interrupts messages between one or both eyes and the brain during a child's visual development. It typically affects one eye rather than both and affects the sight in the weaker eye.

Another underlying condition usually causes lazy eye, such as squint (strabismus), and refractive errors such as near-sightedness, long-sightedness, and astigmatism.

Lazy eye in adults

Lazy eye develops in childhood but may not always be diagnosed at an early enough age for amblyopia treatment to be effective, meaning some adults live with lazy eye. Many adults learn to compensate for their weaker eye if the vision is good in the unaffected eye.

Symptoms of a lazy eye

Lazy eye often doesn't cause symptoms, especially in young children who may not be aware of a problem with their vision or be able to explain it if they are. Older children might be aware they can't see as easily with one eye as the other or have problems with reading or schoolwork because it causes less clear vision.

An underlying eyesight problem causing a lazy eye may become noticeable. A squint, for example, can cause one eye to look in a different direction from the other. Uncorrected refractive errors can cause signs and symptoms such as:

• Eyestrain
• Headaches
• Head tilting
• Poor depth perception
• Needing to sit close to the television or board at school

Untreated, the condition can cause behaviours mistaken for other problems, such as learning difficulties. If your child has difficulties with reading, close up work, or using screens, it's worth having their eyesight checked. Amblyopia can sometimes only be detected by an eye test.

Lazy eye causes

Usually, light travels to the back of the eye, where the retina sends nerve signals to the brain to produce the image we see. In childhood, this pathway from the eye to the brain is developing and learning to produce the vision we'll have as adults.

When something affects the quality of images received by the retina, a lazy eye can develop. A problem with images in one eye can make the brain rely on the other stronger eye for vision.

There is usually an underlying reason for a problem with images in the eye, which helps to describe the type of amblyopia. For example, refractive amblyopia can be caused by a child being longsighted in one or both eyes. Other causes include astigmatism or a marked difference in refraction between the two eyes. All these refractive errors affect the way the eye focuses light.

Lazy eye often doesn't cause symptoms, and young children may not be aware of problems with their sight or may be unable to explain them. Children with eyesight problems that can lead to amblyopia might:

• Find reading or seeing the board or screen at school difficult
• Have a noticeable squint
• Experience headaches and eye strain
• Rub their eyes a lot
• Have problems with co-ordination and judging distances

Lazy eye risk factors

Children with an underlying eye condition that has not been diagnosed and treated are at risk of developing a lazy eye. These conditions include:

• Refractive errors including long-sightedness, near-sightedness (myopia), and astigmatism
• A problem that blocks light into one eye, such as a cataract
• Squint (strabismus)

Other risk factors that can increase the chance of a child having a lazy eye include:

• Premature birth
• Family history of lazy eye

Lazy eye treatment

Lazy eye treatments usually involve two steps. Treatment for any underlying eyesight problem, and treatment for lazy eye itself.

Different children tolerate different treatments, and your child's eye doctor should talk to you about the best plan for your child.

When thinking about how to treat lazy eye, the choice depends on what works best for your child. What matters is consistency and persevering to get positive results.