Amblyopia (also called lazy eye) is a type of poor vision that affects only one eye. It develops when there is a malfunction in the way the brain and eye work together, and the brain cannot recognize the vision of one eye. Over time, the brain increasingly relies on the other, stronger eye, while vision in the weaker eye gets worse.

It's called "lazy eye" because the stronger eye works better. But people with amblyopia are not lazy and cannot control the way their eyes work.

Amblyopia starts in childhood and is the most common cause of vision loss in children. A maximum of 3 in 100 children have it. The good news is that early treatment works well and usually prevents long-term vision problems.

Symptoms of amblyopia can be difficult to notice. Children with amblyopia can have a poor perception of depth - they have a hard time telling how close or far something is. Parents may also notice signs that their child is having trouble seeing clearly, such as:

• Squinting
• 1 eye close
• Tilt their heads

In many cases, parents are unaware that their child has amblyopia until a doctor makes the diagnosis during an eye exam. It is therefore important that all children between the ages of 3 and 5 undergo a visual screening at least once.

Some children are born with amblyopia and others develop it later in childhood. Amblyopia is more likely in children who:

• Are born prematurely (premature)
• Were smaller than average at birth
• Have a family history of amblyopia, cataracts in children, or other eye conditions
• Having developmental disorders

In many cases, doctors don't know the cause of amblyopia. But sometimes another vision problem can lead to amblyopia.

Normally, the brain uses nerve signals from both eyes to see. But if an eye condition worsens vision in 1 eye, the brain may try to work around it. It starts "turning off" signals from the weaker eye and relies only on the stronger eye.

Some eye conditions that can lead to amblyopia include:

• Refractive Errors. These include common vision problems such as myopia (difficulty seeing far away), farsightedness (difficulty seeing things up close) and astigmatism (which can cause blurred vision). Normally these problems are easy to solve with glasses or contact lenses. But if left untreated, the brain can start to rely more on the eye with stronger vision.

• Strabismus . Usually the eyes move together as a pair. But in children with strabismus, the eyes don't line up. An eye can float in, out, up, or down.
• Cataract. This causes cloudiness in the lens of the eye, making things look blurry. Although most cataracts occur in older people, babies and children can also develop cataracts.

As part of a normal vision screening , your child's doctor will look for signs of amblyopia. All children 3 to 5 years old should have their eyesight checked at least once.

If there is a vision problem causing amblyopia, the doctor can treat it first. For example, doctors may recommend glasses or contact lenses (for children who are nearsighted or farsighted) or surgery (for children with cataracts).

The next step is to retrain the brain and force it to use the weaker eye. The more the brain uses it, the stronger it gets. Treatments include:

After your child starts treatment, vision may get better within a few weeks. But it will likely take months to get the best results. After that, your child may need to use these treatments from time to time to prevent amblyopia from returning.

It's important to treat children with amblyopia early - the sooner the better. Children who grow up without treatment can have lifelong vision problems. Amblyopia treatment is usually less effective in adults than in children.