Amblyopia

The information provided in this Resource Guide was developed by the National Eye Institute to help patients and their families search for general information about amblyopia. An eye care professional who has examined the patient's eyes and is familiar with his or her medical history is the best person to answer specific questions.

Other Names

Lazy eye

What is amblyopia?

The brain and the eye work together to produce vision. Light enters the eye and is changed into nerve signals that travel along the optic nerve to the brain. Amblyopia is the medical term used when the vision in one of the eyes is reduced because the eye and the brain are not working together properly. The eye itself looks normal, but it is not being used normally because the brain is favoring the other eye. This condition is also sometimes called lazy eye.

How common is amblyopia?

Amblyopia is the most common cause of visual impairment in childhood. The condition affects approximately 2 to 3 out of every 100 children. Unless it is successfully treated in early childhood, amblyopia usually persists into adulthood, and is the most common cause of monocular (one eye) visual impairment among children and young and middle-aged adults.

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What causes amblyopia?

Amblyopia may be caused by any condition that affects normal visual development or use of the eyes. Amblyopia can be caused by strabismus, an imbalance in the positioning of the two eyes. Strabismus can cause the eyes to cross in (esotropia) or turn out (exotropia). Sometimes amblyopia is caused when one eye is more nearsighted, farsighted, or astigmatic than the other eye. Occasionally, amblyopia is caused by other eye conditions such as cataract.

How is amblyopia treated in children?

Amblyopia treatment is most effective when done early in the child's life, usually before age 7. Treating amblyopia involves making the child use the eye with the reduced vision (weaker eye). Currently, there are two ways used to do this:

Atropine
A drop of a drug called atropine is placed in the stronger eye once a day to temporarily blur the vision so that the child will prefer to use the eye with amblyopia. Treatment with atropine also stimulates vision in the weaker eye and helps the part of the brain that manages vision develop more completely.

Patching
An opaque, adhesive patch is worn over the stronger eye for weeks to months. This therapy forces the child to use the eye with amblyopia. Patching stimulates vision in the weaker eye and helps the part of the brain that manages vision develop more completely.

Can amblyopia be treated in adults?

During the first six to nine years of life, the visual system develops very rapidly. Complicated connections between the eye and the brain are created. We do not yet have the technology to create these eye-to-brain connections in older children and adults.

Scientists are exploring whether treatment for amblyopia in older children and adults can improve vision.

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National Eye Institute-Supported Research

The NEI is currently supporting the Amblyopia Treatment Study: Occlusion Versus Pharmacologic Therapy for Moderate Amblyopia (ATS) to determine whether patching or eyedrops is a better treatment for amblyopia. Recent results for the ATS found that the atropine eyedrops, when placed in the unaffected eye once a day, work as well as eye patching and may encourage better compliance. The study was conducted at 47 clinical sites throughout North America. Read more about the ATS.

In addition, A Randomized Trial Comparing Part-time Versus Minimal-time Patching for Moderate Amblyopia (Two v. Six) is being conducted to determine whether the visual acuity improvement obtained with part-time (6 hours) patching is equivalent to the visual acuity improvement obtained with minimal patching (2 hours) for moderate amblyopia. Recent findings show that patching the unaffected eye of children with moderate amblyopia for two hours daily works as well as patching the eye for six hours. Shorter patching time should lead to better compliance with treatment and improved quality of life for children with amblyopia. Read more about the Two v. Six study.

The NEI is also supporting other clinical studies on amblyopia:

An Evaluation of Treatment of Amblyopia in Children 7 To 18 Years Old

An Observational Study on Recurrence of Amblyopia After Discontinuation of Treatment

A Randomized Trial Comparing Daily Atropine Versus Weekend Atropine

A Randomized Trial Comparing Part-time Versus Full-time Patching for Severe Amblyopia

Vision in Preschoolers (VIP) Study

Resources

The following organizations may be able to provide additional information on amblyopia:

National Eye Institute
2020 Vision Place
Bethesda, MD 20892-3655
(301) 496-5248
http://www.nei.nih.gov/
Conducts and supports vision research. Part of the National Institutes of Health.

American Academy of Ophthalmology
P.O. Box 7424
San Francisco, CA 94120-7424
(415) 561-8500
http://www.aao.org
Represents board-certified ophthalmologists in the United States. Provides information for the public on amblyopia.

American Association for Pediatric Ophthalmology and Strabismus
P.O. Box 193832
San Francisco, CA 94119-3832
(415) 561-8505
http://www.aapos.org
Represents ophthalmologists that specialize in providing eye care for children.

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American Optometric Association
243 N. Lindbergh Boulevard
St. Louis, MO 63141
(314) 991-4100
http://www.aoa.org
Represents optometrists in the United States. Provides information for the public on amblyopia.

The Eye Patch Club
Prevent Blindness America
500 East Remington Road
Schaumburg, Illinois 60173
1-800-331-2020
http://www.preventblindness.org/children/EyePatchClub.html

For additional information, you may wish to contact a local library.

Medical Literature

Below is a sample of the citations available through MEDLINE/PubMed, a service of the National Library of Medicine. MEDLINE/PubMed provides access to over 11 million medical literature citations from 1966 to the present and includes links to many sites providing full text articles and other related resources. You can conduct your own free literature search by accessing MEDLINE through the Internet at http://medlineplus.nlm.nih.gov/hinfo.html. You can also get assistance with a literature search at a local library.

To obtain copies of any of the articles listed below, contact a local community, university, or medical library. If the library you visit does not have a copy of a desired article, you may usually obtain it through an inter-library loan.

Please keep in mind that articles in the medical literature are usually written in technical language. We encourage you to share any articles you order with a health care professional who can help you understand them.

A randomized trial of patching regimens for treatment of moderate amblyopia in children. The Pediatric Eye Disease Investigator Group. Jaeb Center for Health Research, Tampa FL. Arch Ophthalmol 121:603-611, 2003.
In a randomized multicenter (35 sites) clinical trial, 189 children younger than 7 years with amblyopia in the range of 20/40 to 20/80 were assigned to receive either 2 hours or 6 hours of daily patching combined with at least 1 hour of near visual activities during patching. When combined with prescribing 1 hour near visual activities, 2 hours of patching produces an improvement in visual acuity that is of similar magnitude to the improvement produced by 6 hours of daily patching in treating moderate amblyopia in children aged 3 to 7 years.

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A randomized trial of atropine vs patching for treatment of moderate amblyopia in children. The Pediatric Eye Disease Investigator Group. Jaeb Center for Health Research, Tampa FL. Arch Ophthalmol 120:268-278, 2002.
Amblyopia is the most common cause of monocular visual impairment in both children and young and middle-age adults. In a randomized clinical trial, 419 children younger that 7 years with amblyopia and visual acuity in the range of 20/40 to 20/00 were assisted to receive with patching or atropine eye drops at 47 clinical centers. Atropine and patching produce improvement of similar magnitude, and both are appropriate modalities for the initial treatment of moderate amblyopia in children aged 3 to less than 7 years.

The amblyopia treatment study visual acuity testing protocol. Holmes JM, Beck RW, Repka MX, Leske DA, Kraker RT, Blair RC, Moke PS, Birch EE, Saunders RA, Hertle RW, Quinn GE, Simons KA, Miller JM and the Pediatric Eye Disease Investigator Group. Mayo Clinic, Rochester, MN. Arch Ophthalmol 119:1345-53, 2001
This article evaluates the reliability of a new visual acuity testing protocol for children using isolated surrounded HOTV optotypes (letters used for testing). After initial pilot testing and modification, the protocol was evaluated using the Baylor-Video Acuity Tester (BVAT) to present isolated surrounded HOTV optotypes. At 6 sites, the protocol was evaluated for testability in 178 children aged 2 to 7 years and for reliability in a subset of 88 children. Twenty-eight percent of the 178 children were classified as having amblyopia. Using the modified protocol, testability ranged from 24 percent in 2-year-olds to 96 percent in 5- to 7-year-olds. Test-retest reliability was high (r = 0.82), with 93 percent of retest scores within 0.1 logMAR unit of the initial test score. The 95 percent confidence interval for an acuity score was calculated to be the score +/-0.125 logMAR unit. For a change between 2 acuity scores, the 95 percent confidence interval was the difference +/-0.18 logMAR unit. The visual acuity protocol had a high level of testability in 3- to 7-year-olds and excellent test-retest reliability. The protocol has been incorporated into the multicenter Amblyopia Treatment Study and has wide potential application for standardizing visual acuity testing in children.

Amblyopia: detection, prevention, and rehabilitation. LaRoche GR. Division of Ophthalmology, IWK Health Center, Halifax, Nova Scotia, Canada. Curr Opin Ophthalmol 12(5):363-7, 2001.
This year's literature on the detection, prevention, and rehabilitation of amblyopia is again somewhat dominated by the topic of vision screening, specifically photoscreening and also by the therapeutic challenges of compliance and late treatment. Basic scientists also have added to our knowledge and understanding of certain interesting and clinically significant characteristics of the visual perception of people with amblyopia.

The role of drug treatment in children with strabismus and amblyopia. Chatzistefanou KI, Mills MD. Department of Ophthalmology and Visual Sciences, University of Wisconsin-Madison Medical School. Paediatr Drugs 2(2):91-100, 2000.
Strabismus, or misalignment of the eyes, is a common ophthalmic problem in childhood, affecting 2 to 5 percent of the preschool population. Amblyopia is an important cause of visual morbidity frequently associated with strabismus, and both conditions should be treated simultaneously. Pharmacological means for treating strabismus and amblyopia can be divided into 3 categories: paralytic agents (botulinum toxin) used directly on the extraocular muscles to affect eye movements; autonomic agents (atropine, miotics) used topically to manipulate the refractive status of the eye and thereby affect alignment, focus and amblyopia; and centrally acting agents, including levodopa and citicoline, which affect the central visual system abnormalities in amblyopia. In amblyopia therapy, atropine is used to blur vision in the non-amblyopic eye and offers a useful alternative to traditional occlusion therapy with patching, especially in older children who are not compliant with patching.

Successful amblyopia therapy initiated after age 7 years: compliance cures. Mintz-Hittner HA, Fernandez KM. Department of Ophthalmology and Visual Science, University of Texas Houston Medical School. Arch Ophthalmol 118(11):1535-41, 2000.
This article reports successful therapy for anisometropic and strabismic amblyopia initiated after age 7 years. A consecutive series of 36 compliant children older than 7 years (range, 7.0 to 10.3 years; mean, 8.2 years) at initiation of amblyopia therapy for anisometropic (19 patients; mean age, 8.3 years), strabismic (9 patients; mean age, 8.0 years), or anisometropic and strabismic (8 patients; mean age, 8.0 years) amblyopia was studied. Initial (worst) visual acuities were between 20/50 and 20/400 (log geometric mean, -0.83 [antilog, 20/134] for all patients; -0.88 [antilog, 20/151] for anisometropic patients; -0.70 [antilog, 20/100] for strabismic patients; and -0.88 [antilog, 20/151] for anisometropic and strabismic patients). Initial (worst) binocularity was absent or reduced in all cases. Therapy consisted of (1) full-time standard occlusion (21 patients; mean age, 8.0 years), (2) total penalization (7 patients; mean age, 7.8 years), or (3) full-time occlusive contact lenses (8 patients; mean age, 8.8 years). Final (best) visual acuities were between 20/20 and 20/30 for all 36 patients. Final (best) binocularity was maintained or improved for 22 (61 percent) of 36 patients, including 16 anisometropic patients (84 percent), 2 strabismic patients (22 percent), and 4 anisometropic and strabismic patients (50 percent). Given compliance, therapy for anisometropic and strabismic amblyopia can be successful even if initiated after age 7 years.

The National Eye Institute (NEI), part of the National Institutes of Health (NIH), is the Federal government's principal agency for conducting and supporting vision research. Inclusion of an item in this Information Resource Guide does not imply the endorsement of the NEI or the NIH.

National Eye Institute
2020 Vision Place
Bethesda, MD 20892-3655
(301) 496-5248
www.nei.nih.gov