Originally published by Harvard Health.
What Is It?
Lazy eye, also called amblyopia, is an eye problem that can occur in growing children. In the typical child with lazy eye, the right and left eyes have significantly different qualities of vision, so that the images produced by one eye are weak or distorted compared with the images produced by the other eye. Because the weak eye sends poorly focused images to the brain, the brain learns to depend on the stronger eye for its visual information. If this situation is not corrected, the brain eventually chooses to accept images from the stronger eye alone and ignores images from the weak one. In other words, the weak eye doesn’t learn to see.
The brain’s choice usually is made early in childhood when the brain’s visual pathways are still developing. This critical period begins at birth and probably ends sometime between ages 6 and 9. If lazy eye is not diagnosed and treated within this critical period, the brain may choose to ignore the weak eye permanently, causing a lifelong loss of vision on that side.
Lazy eye has several causes, including:
- Crossed eyes (strabismus) — Children with crossed eyes often have double vision (diplopia) when they use both eyes at the same time. To prevent this, a child may consistently focus with one eye more than the other.
- Problems related to severe nearsightedness or farsightedness — When a child has nearsightedness (distant objects look blurry) or farsightedness (nearby objects look blurry), the problem may not affect both eyes equally. For example, one eye may have perfectly normal vision, while the other is blurred; or both eyes may be blurred, but one is worse than the other. In either situation, the brain gradually learns to ignore visual images from the eye that has poorer vision.
- Structural problems — Sometimes, a growing child’s vision is blocked by a structural problem of the eye or eyelid. Common examples include a congenital cataract (an opaque area that develops inside the lens of the eye before birth), a scar on the cornea or congenital ptosis (a drooping eyelid that is present at birth).
In the United States, lazy eye affects an estimated 1% to 2% of the population. In rare cases, the brain ignores both eyes because both produce blurry images. This can cause permanent blindness in both eyes.
Lazy eye usually does not cause any symptoms. Sometimes parents suspect vision problems because a child squints, looks cross-eyed, or holds his or her head in awkward positions to see things. In many cases, the problem is detected by a routine vision screening exam, either before or after a child starts school. The screening exam will show that the child’s vision is much better in one eye than the other.
If the results of a screening exam suggest that your child has lazy eye, your primary care doctor will refer you to an ophthalmologist, a doctor who specializes in eye disorders. The ophthalmologist will confirm the diagnosis by doing a thorough eye examination, including separate tests of how well each eye sees. As part of the diagnostic process, the ophthalmologist will inspect your child’s eyes for structural abnormalities, check eye alignment to rule out crossed eyes, and assess movement of the eye muscles.
Lazy eye begins early in childhood. It should be treated as soon as possible. Without proper treatment, the condition can produce profound loss of vision that lasts a lifetime.
To prevent permanent loss of vision in a weak eye, the causes of lazy eye must be identified and treated as early as possible during childhood. Make sure your newborn receives a thorough eye exam within the first few days after delivery. This exam will check for any obvious abnormalities involving the structure of your child’s eyes or eyelids. As your child grows, a doctor should check your child’s eyes as a part of every “well-child” visit. Your child should have more formal vision testing, using pictures, letters or numbers, beginning no later than age 3, and at regular intervals after that. There are now techniques that allow detection of amblyopia even when the infant is pre-verbal.
Treatment of lazy eye has two goals:
- Produce clear vision in both eyes — Depending on the cause of your child’s lazy eye, this can be done with prescription eyeglasses to correct severe focusing problems; surgery and eye muscle exercises to realign crossed eyes; and surgery to correct any structural problem of the eye or eyelid that is blocking normal vision.
- Strengthen the weak eye — The most common treatment is to have the child wear a patch over the stronger eye for a certain number of hours each day. In many cases, the doctor will recommend that the patch first be worn for the entire day.) This daily patching typically continues for at least six months. Your child’s progress will be monitored with frequent eye exams. Once your child’s vision has become normal, occasional patching may be necessary until about age 10. As an alternative to patching, some doctors use an opaque contact lens. Others prescribe atropine eye drops (Atropine-Care and other brand names) to blur vision temporarily in the stronger eye.
When To Call A Professional
Make an appointment to see your pediatrician or ophthalmologist if your child:
- Appears cross-eyed
- Holds his or her head in an abnormal position while looking at something in the distance — The child tilts the chin up, looks down his or her nose, faces one eye forward or uses some other unusual posture to compensate for a vision problem.
- Squints often — Squinting temporarily corrects blurred vision, so it can be a sign that your child’s eyes are not focusing properly.
- Consistently covers or closes one eye — Crossed eyes cannot work together without causing double vision, so if your child has crossed eyes he or she may eliminate the problem by blocking the vision in one eye. Conversely, if a child objects to having one eye covered but does not object to having the other eye covered it may be a sign that one eye does not see well.
Also, make an appointment if your child’s school notifies you that your child’s vision exam was abnormal.
The outlook is good if the condition is treated early. Proper treatment during early childhood often produces near normal vision in the affected eye.
In the past, some doctors have offered a poor prognosis for treating lazy eye in children over age 12, or even younger. However, new evidence suggests that the outlook for lazy eye may be improved with prompt, appropriate treatment regardless of the age at which it is diagnosed. There have been cases in which teenagers and even middle-aged adults with lazy eye have recovered vision in the weak eye.
National Eye Institute
2020 Vision Place
Bethesda, MD 20892-3655
American Academy of Ophthalmology
P.O. Box 7424
San Francisco, CA 94120
Phone: (415) 561-8500
American Academy of Pediatrics (AAP)
141 Northwest Point Blvd.
Elk Grove Village, IL 60007-1098
Phone: (847) 228-5005