Why do lazy eyes develop

Lazy eye develops because of abnormal visual experience early in life that changes the nerve pathways between a thin layer of tissue retina at the back of the eye and the brain. The weaker eye receives fewer visual signals. Eventually, the eyes' ability to work together decreases, and the brain suppresses or ignores input from the weaker eye.

Anything that blurs a child's vision or causes the eyes to cross or turn out can result in lazy eye. Common causes of the condition include:. Difference in sharpness of vision between the eyes refractive amblyopia. A significant difference between the prescriptions in each eye — often due to farsightedness but sometimes to nearsightedness or an uneven surface curve of the eye astigmatism — can result in lazy eye.

Glasses or contact lenses are typically used to correct these refractive problems. In some children lazy eye is caused by a combination of strabismus and refractive problems. Mayo Clinic does not endorse companies or products. Advertising revenue supports our not-for-profit mission. This content does not have an English version. If that eye is not stimulated properly, the nerve cells responsible for vision do not mature normally.

In the United States, amblyopia affects approximately 2 percent of all children. It is the most common cause of partial or total blindness in one eye in the U.

In fact, it is a developmental problem in the nerve connecting the eye to the brain, not a problem in the eye itself. After a child is 8 years old, the likelihood of vision improvement drops significantly but can still be effective. Many children who have unequal vision, or anisometropia, do not know they have an eye problem because the stronger eye and the brain compensate for the shortfall.

The weaker eye gets progressively worse, and amblyopia develops. Glasses: A child with near-sightedness, far-sightedness, or astigmatism will be prescribed glasses.

The child will have to wear them all the time so that the specialist can monitor how effective they are at improving the vision problems in the lazy eye. Glasses may also correct an eye turn. Sometimes, glasses can solve the amblyopia, and no more treatment is required. They need to be encouraged to wear them for the treatment to be effective. Cataract surgery, or phacoemulsification: If a cataract is the cause of amblyopia, it can be surgically removed under either local or general anesthesia.

Correcting droopy eyelids: For some people, amblyopia is caused by an eyelid that is blocking the vision to the weaker eye.

In this case, the usual treatment is surgery to lift the eyelid. Once the vision is corrected and any underlying medical issues are addressed, then there are several other actions that can be taken to help improve vision.

As the brain is only getting information from that eye, it will not ignore it. The patch is usually worn for a few hours each day. A child should be encouraged to do close-up activities while wearing the patch, such as reading, coloring, or schoolwork. Atropine eye drops: These may be used to blur vision in the unaffected eye.

Atropine dilates the pupil, resulting in blurring when looking at things close up. This makes the lazy eye work more. Atropine is usually less conspicuous and awkward for the child, compared with a patch, and can be just as effective.

Children who cannot tolerate wearing a patch may be prescribed eye drops instead. Experts say this is helpful for older children. This often helps correct a squint as well. The child is then encouraged to use the affected eye again. This can be done using an eye patch to cover the stronger eye, or eyedrops to temporarily blur the vision in the stronger eye.

Treatment is a gradual process that takes many months to work. If treatment is stopped too soon, any improvement may be lost.

Treatment for lazy eye is most effective for younger children. It's uncertain how helpful it is for children over 8 years of age. Page last reviewed: 16 May Next review due: 16 May It's estimated that 1 in 50 children develop a lazy eye. How to tell if your child has a lazy eye A lazy eye does not usually cause symptoms. However, this is usually a sign of another condition that could lead to a lazy eye, such as: a squint — where the weaker eye looks inwards, outwards, upwards or downwards, while the other eye looks forwards short-sightedness myopia , long-sightedness hyperopia and astigmatism childhood cataracts — cloudy patches that develop in the lens, which sits behind the iris the coloured part of the eye and pupil If your child is too young to tell you how good their vision is, you can check their eyes by covering each eye with your hand, one at a time.

When to get medical advice Lazy eye is often diagnosed during routine eye tests before parents realise there's a problem. Read more about eye tests for children. Read more about diagnosing a lazy eye. Causes of a lazy eye The eyes work like a camera. A lazy eye can be caused by: a reduced amount of light entering the eye a lack of focus in the eye confusion between the eyes — where the 2 images aren't the same such as a squint Left untreated, this can lead to the eye's central vision never reaching normal levels.