Amblyopia, often called "lazy eye," is a vision disorder that usually affects one eye but can sometimes involve both eyes. It develops when the brain and the affected eye do not work together properly, causing the brain to favor the stronger eye and ignore signals from the weaker one. Symptoms can be subtle and may include poor vision in one eye, squinting, shutting one eye, tilting the head, eyes that turn in or out, and difficulty judging depth.

Amblyopia is the most common cause of vision loss in children in the United States, affecting about 2% to 3% of children. It typically develops in early childhood, most often before age 7 or 8, and is a leading cause of monocular (one-eyed) visual impairment in adults.

Amblyopia can be managed effectively, especially when detected and treated early. Most children who are treated can achieve significant improvement in vision and prevent long-term vision problems.

When a child has healthy vision, both eyes send clear, focused images to the brain, which combines the information from each eye to create a single, sharp picture.

If the child has amblyopia, the brain receives blurry or mismatched images from one of the eyes. Over time, the brain begins to ignore images sent from that eye. As a result, the affected eye becomes weaker, and the part of the brain that controls vision does not develop well, causing decreased vision.

Children with amblyopia often do not notice a problem because they function well with the stronger eye and do not notice that anything is wrong, making the condition difficult to detect without an eye exam. If not identified and managed during this time, the vision loss can become permanent.

Amblyopia can have lasting effects on daily activities, including reading, motor skills, and overall quality of life.

Amblyopia develops when the brain does not receive normal visual input from one or both eyes during early childhood. This disruption in visual development occurs in three main ways:

• Refractive errors, which are the most common cause of amblyopia. If the difference in vision between the two eyes is large and not corrected with glasses, the brain may favor clearer images from one eye and ignore blurrier images from the amblyopic eye.
• Strabismus, when the eyes are misaligned and do not point in the same direction. One eye may turn in, out, up, or down. The brain may ignore the image from the misaligned eye, which leads to poor development of vision in that eye.
• Visual deprivation, which arises when something partially or completely blocks light from entering the affected eye, preventing it from creating clear images. Common obstructions include cataracts (cloudiness in the lens), droopy eyelids (ptosis), and corneal opacity (clouding or scarring of the cornea). If not treated early, visual deprivation will lead to severe vision loss.
  

In some cases, the exact cause of amblyopia is not known. However, it always results from abnormal visual experience during the critical period of visual development, which prevents the brain and eye from working together as they should.

Risk factors for amblyopia include:

• Strabismus
• Significant refractive errors (such as nearsightedness, farsightedness, or astigmatism)
• Anisometropia (a large difference in refractive error between the two eyes)
• Cataracts
• Droopy eyelids
• Corneal opacity
• Premature birth
• Low birth weight or being small for gestational age
• Family history of amblyopia, strabismus, childhood cataracts, or childhood glaucoma
• Developmental delays
• Delays in visual or neurological development
• Uveitis (inflammation of the uvea, the middle layer of the eye)
• Maternal smoking, alcohol, or drug use during pregnancy
• Certain syndromes or conditions with ocular involvement, such as Down syndrome or cerebral palsy
  

Symptoms of amblyopia may include:

• Poor vision in one eye
• Eyes that turn in or out
• Squinting
• Shutting or covering one eye
• Tilting the head
• Poor depth perception
• Reduced contrast sensitivity
• Poor hand-eye coordination or motor skills
• Slower reading speed
• Preference for using one eye over the other
• Objection to covering the stronger eye
• Nystagmus (involuntary eye movements)
• White pupil (leukocoria, seen in some cases with cataract)

Sometimes, there are no noticeable symptoms of amblyopia, and the condition is only detected during an eye exam.

To diagnose amblyopia, a doctor will review the child’s medical history, conduct a physical exam, and order one or more diagnostic tests.

The doctor will ask about the child’s symptoms, such as poor vision, squinting, or tilting the head, as well as any family history of eye conditions, including amblyopia, strabismus, or childhood cataracts. The American Academy of Pediatrics recommends checking all children for amblyopia on a regular basis. During a physical exam, the pediatrician will look for signs of vision problems depending on the patient’s age. For infants, pediatricians check for cataracts or other eye problems at birth. For infants and toddlers, they check to see if babies fix or follow toys with their eyes and if the eyes are straight. When they are older, children are screened in different ways:

• Binocular red reflex test: Pediatricians may check for differences in the way light reflects from each eye, which can indicate underlying problems.
• Vision screening: This involves the use of electronic tools to check for a significant refractive error or other signs of amblyopia in toddlers up to age 5.
• Linear visual acuity: This test involves identifying letters or shapes on a chart. It is recommended for children age 5 and older. This test is similar to the one used for adults and can be done when children can identify shapes or letters.

If a pediatrician suspects amblyopia, they will refer the child to a pediatric ophthalmologist, a specialist in eye conditions in children and adolescents.

A pediatric ophthalmologist will do further tests for cataracts, visual acuity, and alignment. These tests may include:

• Best corrected visual acuity: This test measures how well each eye can see with the best possible eyeglass or contact lens correction. A difference of two or more lines between the eyes on an eye test chart, or vision below age-appropriate norms in both eyes, may indicate amblyopia.
• Ocular alignment and motility tests: These tests evaluate how well the eyes move and work together and help detect strabismus.
• Refraction (with or without cycloplegia): This test determines if refractive errors such as nearsightedness, farsightedness, or astigmatism are present. Cycloplegia is the temporary paralysis of the muscles that focus the eye. During a cycloplegic refraction exam, an eye physician uses medicated eye drops to induce cycloplegia, which allows for accurate measurement of refractive error.
• Dilated eye exam: In this exam, the physician examines the internal structures of the eye to identify any abnormalities, such as cataracts or other causes of visual deprivation.
  
  Depending on the child’s age, fixation preference testing (to determine which eye a child prefers to use to focus on a target) or stereoacuity testing (to assess depth perception) may be used.

Amblyopia may be effectively treated when treatment is started early in childhood. The main goal of treatment is to improve vision in the weaker eye and help both eyes work together. Treatment plans are tailored to each child based on the cause of amblyopia, age, and how well they respond to therapy.

Main treatments include:

• Correcting underlying vision problems: Glasses or contact lenses are used to correct refractive errors such as nearsightedness, farsightedness, or astigmatism.
• Patching (occlusion therapy): An eye patch is placed over the stronger eye for a set number of hours each day, forcing the brain to use the weaker eye and strengthen its vision.
• Atropine eye drops: These drops are placed in the stronger eye to temporarily blur its vision, encouraging the brain to rely on the weaker eye. This can be an alternative to patching, especially for children who have difficulty wearing a patch.
• Binocular digital therapy: Computer-based games or activities are designed to encourage both eyes to work together and improve vision in the weaker eye. This therapy is often used in children with mild to moderate amblyopia.
• Bangerter filters: These are special filters placed on the lens of glasses over the stronger eye to blur its vision, similar to patching or atropine drops.
• Surgery: In some cases, surgery may be needed to correct the underlying cause of amblyopia, such as removing a cataract or correcting ptosis or strabismus. Surgery is usually followed by other treatments to improve vision in the weaker eye.
  

Treatment is most effective when started early, but some older children may still benefit. Follow-up appointments are important to check progress and, if necessary, adjust treatment.

People with amblyopia may be at increased risk for certain complications, including:

• Permanent vision loss in the affected eye if not treated early
• Reduced depth perception, making it harder to judge distances
• Poor contrast sensitivity, which can affect the ability to see fine details
• Impaired hand-eye coordination and motor skills
• Slower reading speed
• Difficulty with fine visual tasks
• Increased risk of injury or falls due to impaired vision
• Lower self-esteem and quality of life, especially in children
• Vision loss in the stronger eye
• Recurrence of amblyopia after treatment
• Development or worsening of strabismus

If amblyopia is not treated in childhood, it can limit job options that require good vision in both eyes.

Early detection and treatment, especially before age 7, offer the best chance for significant improvement in vision, and many children treated before age 5 can achieve vision close to normal. However, if amblyopia is not identified and managed during the critical period of visual development, vision loss in the affected eye may become permanent. Even after successful treatment, some people may continue to have challenges such as reduced depth perception, slower reading speed, or difficulties with fine visual tasks. There is also a risk that amblyopia can return, especially within the first year after stopping treatment, so regular follow-up is important.

“Yale Pediatric Ophthalmology is a regional center of excellence for management of amblyopia,” says Martha Howard, MD, a Yale Medicine pediatric ophthalmologist. “We are available in seven locations from Greenwich to Waterford and offer the most up-to-date treatments to maximize your child’s vision in a caring, compassionate way.”

Yale Pediatric Ophthalmology, she adds, is a participant in a national Pediatric Eye Disease Investigator Group study evaluating the efficacy of binocular amblyopia treatment using Luminopia, a treatment that uses virtual reality headsets. The study seeks to answer the question of whether children ages 4 to 7 watching shows using the Luminopia headset for one hour per day, six days per week, is as effective as traditional patching.

This article was medically reviewed in July 2026.