Symptoms and causes

Symptoms

Signs and symptoms of lazy eye include:

  • An eye that wanders inward or outward
  • Eyes that appear to not work together
  • Poor depth perception
  • Squinting or shutting an eye
  • Head tilting
  • Abnormal results of vision screening tests

Sometimes lazy eye is not evident without an eye exam.

When to see a doctor

See your child's doctor if you notice his or her eye wandering at any time after the first few weeks of life. A vision check is especially important if there's a family history of crossed eyes, childhood cataracts or other eye conditions.

For all children, a complete eye exam is recommended between ages 3 and 5.

Causes

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 ability of the eyes 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 may result in lazy eye. Common causes of the condition include:

  • Muscle imbalance (strabismus). The most common cause of lazy eye is an imbalance in the muscles that position the eyes. This imbalance can cause the eyes to cross in or turn out, and prevents them from tracking together in a coordinated way.
  • Difference in sharpness of vision between the eyes (refractive anisometropia). A significant difference between the prescriptions in each eye — often due to farsightedness but sometimes to nearsightedness or an imperfection on the surface of the eye called 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.
  • Deprivation. Any problem with one eye — such as a cloudy area in the lens (cataract) — can deprive a child of clear vision in that eye. Deprivation amblyopia in infancy requires urgent treatment to prevent permanent vision loss. Deprivation amblyopia often results in the most severe amblyopia.

Risk factors

Factors associated with an increased risk of lazy eye include:

  • Premature birth
  • Small size at birth
  • Family history of lazy eye
  • Developmental disabilities

Complications

Untreated, lazy eye can cause permanent vision loss. Lazy eye is the cause of permanent vision loss in 2.9 percent of adults.