Amblyopia, or lazy eye, refers to a unilateral or bilateral decrease of vision, in one or both eyes, caused by abnormal vision development in childhood or infancy. It is a common vision problem in children and is the leading cause of decreased vision among children. Most vision loss is preventable or reversible with the right kind of intervention.
Signs and symptoms
The history should address the following:
Previous history of patching or eye drops
Past compliance with these therapies
Previous ocular surgery or disease
Family history of strabismus or other ocular problems
The physical examination should include the following:
Assessment of visual acuity
Testing for crowding phenomenon (difficulty in distinguishing optotypes that are close together)
Specific testing measures in preverbal children
Evaluation of contrast sensitivity
Neutral density filter testing
Assessment of binocular function
Detection of eccentric fixation
A full eye examination must be performed to rule out ocular pathology.
Anisometropia or refractive errors
See Clinical Presentation for more detail.
Imaging studies that may be helpful when the ocular examination is normal and suspicion of an organic cause exists include the following:
Fluorescein angiography (to assess the retina)
Other tests that may be helpful in diagnosis include the following:
Electrophysiologic studies (investigational; differences noted are controversial)
Spectral-domain optical coherence tomography (SD-OCT) 
See Workup for more detail.
First, rule out an organic cause and treat any obstacle to vision, such as cataract or ptosis, if clinically significant. Next, treat anisometropia and refractive errors. Then, initiate occlusion therapy (to force the use of the amblyopic eye) or penalization therapy.
The following are general guidelines for occlusion therapy:
Patching may be full-time or part-time
Always consider lack of compliance in a child when visual acuity is not improving. Question patients regarding peeking
In addition to adhesive Band-Aid–type patches, consider the use of opaque contact lenses, occluders mounted on spectacles, and adhesive tape or Bangerter foils on glasses
Establishing whether the vision of the better eye has been degraded sufficiently with the chosen therapy
Additional treatment options include the following:
Atropine penalization therapy (also used for maintenance)
Optical blurring through contact lenses or elevated bifocal segments
Treatment of strabismus generally occurs last. The endpoint of strabismic amblyopia is freely alternating fixation with equal vision. Surgery generally is performed after this endpoint has been reached.
Amblyopia refers to a decrease of vision, either unilaterally or bilaterally, for which no cause can be found by physical examination of the eye. The term functional amblyopia often is used to describe amblyopia, which is potentially reversible by occlusion therapy. Organic amblyopia refers to irreversible amblyopia caused by ocular pathology that will limit vision improvement. [1, 2, 4]
Most vision loss from amblyopia is preventable or reversible with the right kind of intervention. The recovery of vision depends on how mature the visual connections are, the length of deprivation, and at what age the therapy is begun. It is important to rule out any organic cause of decreased vision because some diseases may not be easily detectable on routine examination.
Although many types of amblyopia exist, it is believed that their basic mechanisms are the same even though each factor may contribute different amounts to each specific type of amblyopia. In general, amblyopia is believed to result from disuse from inadequate foveal or peripheral retinal stimulation and/or abnormal binocular interaction that causes different visual input from the foveae. 
Three critical periods of human visual acuity development have been determined. [6, 7] During these time periods, vision can be affected by the various mechanisms to cause or reverse amblyopia. These periods are as follows:
The development of visual acuity from the 20/200 range to 20/20, which occurs from birth to age 3-5 years.
The period of the highest risk of deprivation amblyopia, from a few months to 7 or 8 years.
The period during which recovery from amblyopia can be obtained, from the time of deprivation up to the teenage years or even sometimes the adult years.
Whether different visual functions (eg, contrast sensitivity, stereopsis) have different critical periods is not known. In the future, determination of these time frames may help modify treatment of amblyopia.
Prevalence of amblyopia is difficult to assess and varies in the literature, ranging from 1-3.5% in healthy children to 4-5.3% in children with ophthalmic problems. Most data show that about 2% of the general population has amblyopia.
Amblyopia was shown in the Visual Acuity Impairment Survey sponsored by the National Eye Institute (NEI) to be the leading cause of monocular vision loss in adults aged 20-70 years or older. Prevalence of amblyopia has not changed much over the years.
Amblyopia is an important socioeconomic problem. Studies have shown that it is the number one cause of monocular vision loss in adults. Furthermore, persons with amblyopia have a higher risk of becoming blind because of potential loss to the sound eye from other causes.
No racial preference is known.
No gender preference is known.
Amblyopia occurs during the critical periods of visual development. An increased risk exists in those children who are developmentally delayed, were premature, and/or have a positive family history.
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