Lazy eye, or amblyopia, is a condition in which someone experiences poor vision in one eye because the brain relies on the other, healthier, eye to support eyesight. It occurs when abnormal visual development in childhood causes one eye to be weak.
When someone with lazy eye observes an object, their brain ignores signals from the weaker eye and processes information from the other. Vision in the weaker eye grows worse over time.
Amblyopia affects many people but is more prevalent in children than adults. About two to three of every 100 children in the United States experience it, and it mostly strikes kids up to the age of 7.
The condition overwhelmingly affects one eye, and it’s rare that it strikes both eyes. Hallmarks of amblyopia are a wandering eye, eyes that don’t move in synchronicity with each other, excessive squinting and head-tilting.
Eyedrops, corrective glasses and eyeglass filters rank as the most common treatment options for kids.
Signs & Symptoms
Amblyopia is typically associated with vision development in infants, so the symptoms and signs can sometimes be hard to discern.
Parents may notice an eye misalignment. If the child becomes fussy when one eye is covered, this can also indicate that they have amblyopia.
Other possible symptoms may include:
- One of the eyes wanders outward or inward.
- Poor depth perception.
- Head tilting.
- The eyes look like they are not working together.
- Shutting of an eye or squinting.
- Abnormal test results on a vision screening.
In most cases, only one eye is affected, but it is possible for both eyes to have amblyopia.
Medical specialists do not know what causes amblyopia. Eye doctors suggest that vision problems in one eye may be responsible.
For example, if your child develops cataracts (cloudy lens) in only one eye, their brain may rely more on the stronger eye to recognize sight. Amblyopia can develop gradually as a result.
Other potential causes or predisposing factors for lazy eye in kids include:
- Genetics (parents who have had lazy eye)
- Premature birth
- Smaller-than-average babies at birth
- Severe nearsightedness or farsightedness (lazy eye may be avoided by treating these refractive errors early)
- Corneal problems
- Crossed eyes
- Developmental abnormalities
The most common cause of amblyopia are refractive errors that are uncorrected. There are two types of refractive amblyopia.
- Anisometropic amblyopia: This type is a kind of unilateral amblyopia. It occurs when each eye has a distinct refractive error.
- Isoametropic amblyopia: This type occurs when amblyopia affects both eyes due to a similar and significant refractive error. It is a bilateral amblyopia.
The anisometropic type is likely when there is 2.0 D or more anisoastigmatism, 1.0 to 1.5 D or more anisohyperopia, or 3.0 to 4.0 D or more anisomyopia.
The isoametropic type is likely in the presence of 4.0 to 5.0 D or more hyperopia, 5.0 to 6.0 D or more myopia, or 2.0 to 3.0 D or more astigmatism.
When significant astigmatism is the cause of amblyopia, it is called meridional amblyopia.
Early diagnosis is important. If parents notice anything odd with their child’s eyes, they should visit an eye doctor as soon as possible. In general, children should visit a doctor around 6 months of age to get a comprehensive optometric examination.
With early treatment, vision issues in an eye with amblyopia can be adjusted. Often, the child’s vision can be fully corrected.
During a comprehensive eye exam, the doctor will do the following:
- Take a complete patient history, including information about family history.
- Test for visual acuity, usually via the Snellen test.
- Evaluate depth perception, eye muscle movement, pupil response to light, color vision, and peripheral vision.
- Look at the cornea’s curvature using keratometry.
- Conduct eye teaming, focusing, and movement testing.
- Do refraction testing to evaluate how much lens power is needed to compensate for various refractive errors that may be present. This is done using a variety of lenses and a phoropter.
If a doctor suspects amblyopia, they may do additional testing to get an accurate diagnosis. If the person is an infant or small child, the parent will play a major role in answering questions and providing information that is important to ensure an accurate diagnosis.
- If the child is at least 3 years old, letters and pictures can be used to evaluate their vision. During the testing, each eye is assessed individually by using an eye patch.
- For kids under age 3, the doctor can use a magnifying device with a light to look for cataracts. Other assessments may be performed to look at the child’s gaze, their ability to fixate, and how well they can follow an object that is moving.
The underlying cause of amblyopia and the condition’s ultimate effect on vision determine the course of treatment. There are various possible treatment methods.
- Corrective eyewear, such as contact lenses or eyeglasses, may be prescribed to people who have refractive errors. These will aid with overall vision.
- Bangerter filters, which go onto an eyeglass lens, may be used. This is placed on the eyeglass lens of the eye that is stronger. The purpose is to blur this eye so the weaker eye is stimulated.
- Eyedrops might be helpful. They can blur the eye that is stronger to help the weaker eye build strength.
- The weaker eye can be stimulated by patching the stronger one.
- In some cases, surgery may help. If the eye muscles are playing a role in this condition, and other methods aren’t effective, surgery may be the next step.
For children, certain activities might be helpful. Puzzles, drawing, and various computer games can all help to strengthen the eyes. These can be used with traditional treatment methods.
Treatment can last 6 to 24 months. Many people notice an improvement in their symptoms within weeks to months.
Even after treatment, it is possible for amblyopia to recur.
It is imperative to receive prompt treatment for this condition. If amblyopia goes untreated, there is a risk for permanent vision loss. In approximately 2.9 percent of adults with permanent vision loss, amblyopia is the cause.
Consult with an optometrist or ophthalmologist if amblyopia is suspected.
Facts About Amblyopia. (September 2013). National Eye Institute.
Types of Amblyopia. (October 2015). American Academy of Ophthalmology.
Amblyopia. All About Vision.
Amblyopia (Lazy Eye). Prevent Blindness.
Amblyopia (Lazy Eye). American Optometric Association.
Lazy Eye (Amblyopia). Mayo Clinic.
Refractive Errors. Kellogg Eye Center.
Comprehensive Eye and Vision Examination. American Optometric Association.
Strabismus and Crossed Eyes. All About Vision.
Facts About Cataracts. National Eye Institute.