What Is Amblyopia? Symptoms, Causes, Diagnosis, Treatment, and Prevention

Amblyopia is decreased vision in one or both eyes that is caused when the visual part of the brain doesn’t develop normally in infants or children.

In early childhood, the brain learns to “see,” or interpret images from the eyes. When a child has amblyopia, a poor image is transmitted from the affected eye, and the brain doesn’t learn to see well.

Vision loss occurs because the nerve pathways between the brain and the “bad” eye are not properly stimulated.

Amblyopia is sometimes called “lazy eye,” but sometimes people also use this term to describe another condition known as strabismus, says Alexandra Williamson, OD, an optometrist at the Cleveland Clinic in Ohio.

“Strabismus is a condition where the eyes don’t align correctly, and one or both eyes drift in another direction rather than straight ahead. Uncorrected strabismus can lead to amblyopia and vice versa — you can have both conditions at the same time,” Dr. Williamson says.

Signs and Symptoms of Amblyopia

There aren’t very many signs or symptoms of amblyopia, and those that do occur can frequently go unnoticed; oftentimes parents don’t know or even suspect there’s a problem until a doctor diagnoses it at an eye exam.

In many cases, children with amblyopia can have poor depth perception, which means they have trouble judging how close or far away something is. Parents or teachers may notice a child with amblyopia squinting, shutting one eye, and tilting their head to try to see clearly.

Causes and Risk Factors of Amblyopia

Sometimes people are born with amblyopia, while others may develop the condition later in childhood.

There are a few factors that increase the risk of having amblyopia.

  • A family history of amblyopia or childhood cataracts
  • Being born prematurely or having a low birth weight
  • Developmental disabilities
The most common cause of amblyopia is refractive error, which is a type of vision problem that makes vision blurry, says Williamson. There are four common types of refractive errors:

  • Nearsightedness (myopia), which makes faraway objects appear blurry
  • Farsightedness (hyperopia), which makes close objects appear blurry
  • Astigmatism, which can make far and near objects look blurry or distorted
  • Presbyopia, which makes it hard for middle-aged and older people to see things up close

Being much more nearsighted or farsighted in one eye at birth or early childhood can cause amblyopia, Williamson says. “For example, if one eye has astigmatism and the other eye doesn’t, then the eye that has the astigmatism is more likely to become amblyopic,” she says.

There are several “critical periods” of development in a person’s life, which is the term used in medicine to describe a point or span of time when the brain is learning a specific skill, says Williamson. “There are several critical periods in the brain that overlap as a child grows into an adult, and the critical period for vision goes from birth until around age 8 to 10, though it’s a little different for every child,” she says.

Williamson explains, “In the critical period for vision, the brain is allocating resources to areas where it thinks it needs stronger connections, and then taking resources away from other areas. If you have one eye that provides clear vision to the brain and one eye that doesn’t, the brain is going to start taking the resources (neurons) away from the bad eye and then reallocate those resources to the other eye, because it gets better information from that eye.”

A less common reason for amblyopia is something blocking the visual pathway altogether, which is called deprivation amblyopia, says Williamson. Although this is rare, if it goes on for a long time, the child may never develop normal vision in the affected eye. Deprivation amblyopia can be caused by a cataract, droopy eyelid, a corneal ulcer, eye injury, or an eye disease such as glaucoma.

How Is Amblyopia Diagnosed?

The best way to detect any eye condition, including amblyopia, is to have an annual eye exam, says Williamson. “The American Optometric Association recommends a screening by a qualified eye doctor between age 6 months and 1 year, again between the ages of 3 and 5, and then annually after that. That’s the guideline for screening for healthy children,” she says.

According to the organization, school screenings miss up to 75 percent of children with vision problems, and 61 percent of the children found to have eye problems through screenings never visit the doctor or get help for the issue.

Tests that help an eye professional diagnose amblyopia include using eye drops to dilate the eyes, shining a light into each eye, covering one eye at a time to test whether each eye can follow a moving object, and having a child read letters or identify images on a chart that’s several feet away.

There are a few things that the eye doctor is looking for during the exam and tests:

  • Do the eyes allow light all the way through?
  • Is the vision the same in both eyes, or is the vision much worse in one eye?
  • Do the eyes track an object correctly, and are they moving together?
  • Are the eyes properly aligned?
  • Does one eye wander or drift?
  • Are there any cataracts that are detected?

“Pediatric eye care providers have various methods that we can use to gain information from patients who are either preverbal, nonverbal, or special needs. We collect a lot of data in ways that might just look like we’re playing with the child,” says Williamson.

Prognosis of Amblyopia

The prognosis of amblyopia can depend on the circumstances and underlying cause of the condition, says Williamson. “The prognosis might be poor or guarded for a child born with a cataract or retinal disease or something that blocks vision at a young age,” she says.

If the cause is due to a refractive error, the prognosis is really dependent on how early it’s diagnosed and treated, says Williamson.

About three out of four children with amblyopia who are treated do show a good return of vision, though about half have a slight decrease in their vision over time.

If amblyopia isn’t diagnosed and treated before the visual system matures, it may become irreversible.

In some cases, older children with amblyopia can still have their vision improved with treatment. After the visual system matures, it’s possible that amblyopia can recur or result in a decrease in visual acuity.

Duration of Amblyopia

“With early intervention, it is possible that amblyopia goes away and doesn’t come back. There are also cases that even with treatment, we can see some residual amblyopia in adulthood,” says Williamson.

Treatment and Medication Options for Amblyopia

Whenever amblyopia is suspected, it’s important to first rule out any causative factors that need to be treated on their own, such as an eye disease, says Williamson.

“The treatment for amblyopia is stepwise: We do one, then the other, then the other; not every patient needs all the treatments. If we see a need for glasses or contacts, that’s the first step. However, even after correcting vision, without further treatment, they still wouldn’t see 20/20,” she says.

An eye patch may be used if one eye has amblyopia and the other does nothing to stimulate the weaker eye, says Williamson. “This forces the brain to work with the bad eye and develop a stronger relationship,” she says.

A Bangerter filter (also called a Bangerter occlusion foil) is a special filter that can be placed on the eyeglass lens of the better eye to block light transmission and reduce visual acuity — it works in the same way as an eye patch.

There are instances where surgery is needed to correct misaligned eyes, remove a cataract, correct glaucoma, or lift a droopy lid.

Medication Options

Sometimes an eye drop called atropine is used as an alternative when patching doesn’t work as well, says Williamson. “The eye drop is meant to blur the good eye — it’s the same premise as the patch: The brain has to rely on the bad eye more,” she says.

Alternative and Complementary Therapies

There isn’t strong evidence that eye exercises help amblyopia, but trying them won’t make the condition worse. The following exercises can be used in conjunction with proven treatments — not as a replacement.

  • Color within the lines in a coloring book.
  • Hold a pencil close to your nose, then move it away, then slowly bring it close. Focus on it as it moves.
  • Do puzzles while wearing an eye patch on the unaffected (stronger) eye.
  • Read while wearing a patch on the unaffected eye.

Prevention of Amblyopia

The number one way to prevent amblyopia is through regular checkups with an eye care professional, says Williamson.

Limiting screen time for children may help prevent amblyopia, she says. “There’s a growing body of evidence describing the negative effects of screens on children’s vision. This generation isn’t running around outside and playing as much as previous generations — they are using smartphones and tablets much more,” says Williamson.

Research out of Ireland found that using screens for more than three hours a day increased the odds of myopia (nearsightedness) in schoolchildren.

Severe myopia may put children at risk for eye problems later in life, including retinal detachment, glaucoma, and macular degeneration.

Practice good visual habits, which include avoiding touching the eyes or eye rubbing, she suggests. “If your child is doing one or both of these, bring them in so we can figure out why and, if necessary, treat it,” says Williamson.

Everything doctors recommend for your overall health is also going to be good for your eyes, she says. “That includes eating lots of fruit and vegetables, regular exercise, and drinking enough water,” says Williamson.

Nutrients, including zinc, lutein, omega-3 fatty acids, and the vitamins A, C, and E, have been found to be beneficial to eye health. Oranges, strawberries, and mangoes have vitamins C and E, which can help restore tissues and prevent infections.

Complications of Amblyopia

If amblyopia isn’t treated early enough, it can result in a permanent visual defect or loss of depth perception. If, later in life, the “good” eye ever gets diseased or injured, a person may have to live the rest of their life with poor vision.

Research and Statistics: Who Has Amblyopia?

Amblyopia starts in childhood, and it’s one of the most common eye conditions, says Williamson. Up to 3 out of 100 children have amblyopia.

The prevalence of amblyopia in preschoolers is about the same across racial and ethnic groups in the United States.

Related Conditions to Amblyopia

Strabismus is an eye condition in which both eyes do not line up in the same direction, which means they don’t look at the same object at the same time. When this happens, it confuses the brain, because two different images, one from each eye, are relayed.

The brain may learn to ignore or suppress the image that comes from the weaker eye, and it can eventually cause amblyopia if it goes untreated.

Resources We Love

American Academy of Ophthalmology is a professional association of eye doctors and surgeons. Its mission is to protect sight and empower lives through patient advocacy, education, and advancing the profession of ophthalmology. The association provides information for patients on EyeSmart.

Children’s Eye Foundation is on a mission to end preventable vision loss in children. The organization provides online resources on finding eyeglasses as well a pediatric ophthalmologist; it also has as a glossary of eye terms and conditions.

EyeCare America offers free eye exams for eligible people over the age of 65 or who are at risk for glaucoma.

National Eye Institute (NEI) was first established by Congress to protect and prolong the vision of the American people. The NEI supports eye disease research through grants and training. It also offers information about eye health for adults and children.

Leave a comment

Your email address will not be published. Required fields are marked *