Lazy eye is when your brain favors one eye, often due to poor vision in your other eye. Eventually, your brain ignores the signals from your weak or “lazy” eye. This can damage vision, especially depth perception.

The medical term for lazy eye is “amblyopia.” Your affected eye doesn’t necessarily look different, although it may “wander” in different directions. That’s where the term “lazy” comes from. The condition will usually only affect one of your eyes, but in certain circumstances, the vision in both of your eyes can be affected.

The condition usually occurs in children. According to the Mayo Clinic, it’s the leading cause of decreased vision among children.

It’s important to note that a lazy eye isn’t the same as a crossed or turned eye. That condition is called strabismus. However, strabismus can lead to amblyopia if your crossed eye gets much less use than your uncrossed one.

If amblyopia goes untreated, temporary or permanent loss of vision can occur. This can include loss of both depth perception and 3-D vision.

Amblyopia may be hard to detect until it becomes severe. Early warning signs include:

  • a tendency to bump into objects on one side
  • an eye that wanders inward or outward
  • eyes that appear not to work together
  • poor depth perception
  • double vision
  • squinting

Amblyopia is related to developmental problems in your brain. In this case, the nerve pathways in your brain that process sight don’t function properly. This dysfunction occurs when your eyes don’t receive equal amounts of use.

A number of conditions and factors can lead you to rely on one eye more than the other. These include:

The eye that you use less becomes weaker (“lazy”) over time.

Amblyopia usually occurs in only one eye. When it first occurs, parents and children often don’t notice the condition. It’s important to get routine eye exams as an infant and child, even if you show no outward symptoms of eye problems.

The American Optometric Association recommends that children have eye exams when they are 6 months old and 3 years old. After that, children should receive routine exams every 2 years, or more frequently, from ages 6 to 18.

Your eye doctor will typically perform a standard eye exam to assess vision in both of your eyes. This involves a series of tests, such as:

  • identifying letters or shapes on a chart
  • following a light with each eye and then both of your eyes
  • having your doctor look at your eyes with a magnifying device

Among other things, your doctor will check your vision clarity, eye muscle strength, and how well your eyes focus. They will look for a wandering eye or differences in vision between your eyes. For most amblyopia diagnoses, an eye examination is all that is required.

Treating underlying eye conditions is the most effective way to treat amblyopia. In other words, you need to help your damaged eye develop normally. Early treatment measures are simple and may include eyeglasses, contact lenses, eye patches, eye drops, or vision therapy.

The earlier you get treatment, the better the outcome. However, recovery may still be possible if your amblyopia is diagnosed and treated when you’re older.

Glasses/contact lenses

If you have amblyopia because you’re nearsighted or farsighted, or have astigmatism in one eye, corrective glasses or contact lenses may be prescribed.

Eye patch

Wearing an eye patch over your dominant eye can help strengthen your weaker eye. Your doctor will probably suggest that you wear the patch 1 to 2 hours a day, depending on how severe your amblyopia is. The patch will help develop your brain area that controls vision.

Eye drops

Drops may be used once or twice a day to cloud your vision in your healthy eye. Like an eye patch, this encourages you to use your weaker eye more. This is an alternative to wearing a patch.

Surgery

If you have crossed eyes or eyes that point in opposite directions, you may require surgery on the muscles of your eye.

Although amblyopia can in some cases result in vision impairment or blindness, it’s typically very treatable, especially when caught early. Talk to a doctor if you think you or your child may have amblyopia.