Lazy Eye (Amblyopia) in Children: Signs, Causes and Treatment

Amblyopia, or lazy eye, is vision that does not develop properly in one eye during childhood, because the brain learns to rely mostly on the other eye. The affected eye can look completely normal. Found early, it is usually treated with glasses, then a patch or drops in the stronger eye.

What is amblyopia (lazy eye)?

It is reduced vision, usually in one eye, caused by vision not developing properly during childhood. The US National Eye Institute (NEI) explains that the brain and the eye stop working well together: the brain cannot properly recognize the image from one eye and relies more and more on the other, while vision in the weaker eye gets worse.

The Canadian Association of Optometrists (CAO) notes that this vision loss cannot be corrected right away with glasses, and that it sometimes affects both eyes. The name "lazy eye" is a little misleading: the eye is not lazy and the child is not in control, the NEI points out, adding that up to 3 in 100 children have it.

What is the difference between amblyopia and strabismus?

Strabismus is a problem with how the eyes line up, while amblyopia is a problem with vision. In strabismus, one eye turns in, out, up or down. In amblyopia, the eye can be perfectly straight, but the brain does not use it enough for it to see clearly.

The two are linked: the NEI and the Mayo Clinic list strabismus among the causes of amblyopia, since the brain ignores the image from the turned eye. But amblyopia can also happen with well-aligned eyes, the American Association for Pediatric Ophthalmology and Strabismus (AAPOS) points out. Our article on strabismus in children and adults covers eye turns and their treatment in detail.

What causes amblyopia?

Anything that keeps one eye from sending a clear image to the brain during childhood. The Mayo Clinic describes three main causes. The first is strabismus. The second is a large difference in prescription between the eyes, often from farsightedness, sometimes from nearsightedness or astigmatism: the blurry eye gets set aside.

The third is deprivation: something blocks the view of one eye, such as a cataract present from birth, according to the CAO and the Mayo Clinic, or a droopy eyelid (ptosis), the American Academy of Ophthalmology (AAO) adds. The CAO notes that amblyopia most often comes from an uncorrected glasses prescription or strabismus. The NEI and the Mayo Clinic add that the risk is higher in children born early or small, in those with a family history and in those with a developmental disability. Our article on farsightedness in children explains what a farsighted eye means.

What signs might parents notice?

Sometimes a child squints or shuts one eye, tilts their head or misjudges distances. The NEI and the Mayo Clinic name these signs, along with an eye that wanders in or out and eyes that do not seem to work together. The CAO adds a head that stays turned or tilted.

Poor depth perception can show in everyday actions: the child has trouble telling whether something is near or far, the NEI explains. An abnormal result on a vision screening is also a sign, according to the Mayo Clinic. None of these signs proves anything on its own, but each is worth an exam.

Why does amblyopia often go unnoticed?

Because the eye that sees well does all the work. The CAO explains that amblyopia usually affects one eye and has no visible signs: the other eye compensates, and the person rarely notices the poorer vision on one side unless the good eye is covered.

So a child does not complain, since they do not know they should see better, and the affected eye can look normal, the AAPOS notes. The AAO adds that parents often do not notice either, unless there is strabismus or another visible eye problem. According to the NEI, many parents only find out at an eye exam.

Why does early detection matter?

Because vision develops in the first years of life, and treatment works better during that time. The AAO says that for good results, amblyopia should be treated before age 7 or 8. The CAO notes that when it is found and treated before 8, it often resolves completely, and that it gets harder to treat with age.

Without treatment, the affected eye can keep reduced vision for life, the NEI and the CAO warn. For screening, the CAO recommends a first eye exam at 6 to 9 months, a second between 2 and 5 years, then a yearly exam from 6 to 19; the NEI and the Mayo Clinic advise at least one screening or exam between ages 3 and 5. At PrimeVision, children are seen from age 4: see our page on children's eye care from age 4.

How is amblyopia found?

By comparing the vision of each eye. According to the Mayo Clinic, from about age 3 the child names pictures or letters while one eye is covered, then the other. The AAO explains that the exam looks for a difference in vision between the two eyes, and also checks for other eye health problems.

Drops are generally used to dilate the pupils, the Mayo Clinic notes; vision may stay blurry for a few hours or a day. In children, these drops also relax focusing, which lets the prescription be measured more accurately: this is cycloplegic refraction, which the AAO recommends in its practice guideline on amblyopia. Our article on your child's first eye exam walks through the visit.

Can glasses alone treat it?

Yes, in some children. The NEI and the CAO explain that the cause is treated first: when amblyopia comes from an uncorrected prescription, glasses are the first step. The AAO practice guideline confirms that correcting the prescription alone can improve vision in the affected eye.

In a Pediatric Eye Disease Investigator Group (PEDIG) study of 84 children aged 3 to 6 with a different prescription in each eye, glasses alone improved vision by at least 2 lines in about 3 children in 4, and the amblyopia went away in about 1 child in 4. The gains took up to 30 weeks. Our article on glasses for kids helps you choose a frame your child will keep on.

How does an eye patch work?

The stronger eye is covered so the brain has to use the weaker eye. The NEI describes a stick-on patch, like a bandage, that some children wear 2 hours a day and others whenever they are awake. The Mayo Clinic mentions 2 to 6 or more hours a day; the optometrist or ophthalmologist sets the time.

In a PEDIG trial of 189 children under 7 with moderate amblyopia, 2 hours of patching a day, combined with at least an hour of close-up activities, gave an improvement similar to 6 hours after 4 months. The AAO advises a patch stuck to the skin around the eye, not a pirate-style patch with an elastic, which is too easy to remove or peek around.

Can atropine drops replace the patch?

For some children, yes. The NEI explains that a daily drop of atropine in the stronger eye temporarily blurs its near vision, which pushes the brain to use the other eye. The Mayo Clinic says the drops are prescribed daily or on weekends, and can cause light sensitivity and eye irritation.

In a PEDIG trial of 419 children under 7 with moderate amblyopia, atropine and patching gave similar gains after 6 months; patching worked a little faster at first. The NEI notes that some parents find drops easier, for example when a young child pulls the patch off. The AAPOS adds that drops may work less well when the stronger eye is nearsighted or the amblyopia is severe.

What are screen-based binocular treatments?

They are treatments in which the child watches videos through a headset or special glasses that show each eye a different image. The AAO describes a virtual reality headset for children aged 4 to 7, and the AAPOS says these treatments are approved in the US but still being studied to learn which types of amblyopia they suit.

In a trial published in 2022 of 105 children aged 4 to 7, the headset used one hour a day, 6 days a week, together with glasses, improved vision in the affected eye by about 1.8 lines in 12 weeks, versus 0.8 lines with glasses alone. A PEDIG trial of a tablet game found it did not do as well as 2 hours of patching a day. If you are interested in this option, the AAO suggests asking the child's ophthalmologist.

How long does treatment last?

Often months, and sometimes a few years. The NEI says vision may start to improve within a few weeks, but full results take months. The Mayo Clinic puts treatment at six months to two years.

The AAO practice guideline generally plans a follow-up visit 2 to 3 months after treatment starts, then adjusts based on the response. Once vision has improved, the AAO notes that part-time patching may be needed for a few years to keep the gains.

Can amblyopia come back after treatment?

Yes, in about 1 child in 4 within the year after stopping. That is what PEDIG found in 145 children under 8 who were successfully treated with patching or atropine, then followed for a year off treatment. The AAO practice guideline cites this figure and recommends follow-up after treatment stops.

In children who wore a patch 6 or more hours a day, it came back more often when patching was stopped all at once than when it was cut to 2 hours before stopping. The AAO also recommends keeping glasses or contacts until visual maturity, usually in the early teens. If amblyopia comes back, treatment starts again, the Mayo Clinic says.

Can amblyopia be treated in teens or adults?

Sometimes in teens, less often in adults. The NEI says treatment is usually less effective in adults than in children, and the AAPOS writes that current treatments do not work for adults. The CAO notes, though, that research on adult amblyopia is moving forward.

For older children, the AAO practice guideline says treatment can still help, especially if there was no treatment before. In a PEDIG trial of 507 young people aged 7 to 17, about half of the 7 to 12-year-olds treated with patching and atropine gained at least 2 lines in 24 weeks, versus about 1 in 4 with glasses alone. In 13 to 17-year-olds, gains showed mostly in those never treated before.

How can you help your child during treatment?

By keeping the routine as simple as you can: glasses every day, the patch during an activity they enjoy, and encouragement. The AAPOS suggests patching during TV, a game, colouring or tablet time, and notes that close-up activities may help. The AAO suggests distracting the child or rewarding them for keeping the patch on.

With a toddler, the AAO suggests practising by putting a patch on a doll, or letting the child decorate the patch. Tell the teacher, who can praise the child. Keep an eye on them on stairs at first, since a patch can make them clumsy. If the skin gets red, try another size or type of patch and change its angle each day, the AAO advises.

Where can you have your child's vision checked in Montréal?

At PrimeVision, 9520 Boulevard de l'Acadie, Suite 222, in Montréal (Ahuntsic), optometrists and a licensed optician work under one roof. Children are seen there from age 4, for an eye exam with an optometrist. When the exam shows that follow-up in ophthalmology is needed, the clinic sends the referral directly and gives you a copy; wait times depend on the hospital or clinic that receives it. The optician makes the child's glasses to their prescription. RAMQ covers eye exams for children under 18 and adults 65+.

To book, go through our page to have each eye's vision compared by an optometrist: book online, the times shown are the open ones.

Sources

• Amblyopia (Lazy Eye), National Eye Institute, November 26, 2024.
• Amblyopia: What Is Lazy Eye?, American Academy of Ophthalmology, November 25, 2025.
• Lazy eye (amblyopia): Symptoms and causes, Mayo Clinic, April 16, 2025.
• Lazy eye (amblyopia): Diagnosis and treatment, Mayo Clinic, April 16, 2025.
• Amblyopia (Lazy Eye), Canadian Association of Optometrists, March 11, 2023.
• Amblyopia Preferred Practice Pattern, Cruz OA et al., American Academy of Ophthalmology, Ophthalmology, 2023, updated February 2024.
• Treatment of anisometropic amblyopia in children with refractive correction, Cotter SA et al., Pediatric Eye Disease Investigator Group, Ophthalmology, 2006.
• A randomized trial of patching regimens for treatment of moderate amblyopia in children, Repka MX et al., Pediatric Eye Disease Investigator Group, Archives of Ophthalmology, 2003.
• A randomized trial of atropine vs. patching for treatment of moderate amblyopia in children, Pediatric Eye Disease Investigator Group, Archives of Ophthalmology, 2002.
• Randomized Controlled Trial of a Dichoptic Digital Therapeutic for Amblyopia, Xiao S et al., Ophthalmology, 2022.
• Effect of a Binocular iPad Game vs Part-time Patching in Children Aged 5 to 12 Years With Amblyopia, Holmes JM et al., Pediatric Eye Disease Investigator Group, JAMA Ophthalmology, 2016.
• Risk of amblyopia recurrence after cessation of treatment, Holmes JM et al., Pediatric Eye Disease Investigator Group, Journal of AAPOS, 2004.
• Randomized trial of treatment of amblyopia in children aged 7 to 17 years, Scheiman MM et al., Pediatric Eye Disease Investigator Group, Archives of Ophthalmology, 2005.
• Amblyopia, American Association for Pediatric Ophthalmology and Strabismus, updated January 2024.