What is amblyopia?
Amblyopia (sometimes called “lazy eye”) results from abnormal development of vision in early childhood. In amblyopia, one eye develops proper vision, while the other eye (the amblyopic eye) fails to develop normal vision.
What causes amblyopia?
An infant is not born with a fully developed visual system. Rather, vision improves, changes, and develops during the first nine years of life. If the eyes do not function normally during this critical period, the visual system does not receive the input that it needs to develop properly. If the eyes function unequally during this period, amblyopia can occur.
Three major causes of abnormal eye function that can lead to amblyopia include:
Strabismus (wandering/crossed eyes)
In strabismus, the brain learns to ignore the wandering eye in order to avoid double vision. The good eye develops normal vision while the wandering eye becomes amblyopic.
Unequal Focusing of Eyes (refractive error)
In unequal focusing, one eye is out of focus because it is more short-sighted, long-sighted, or astigmatic than the other eye. As in strabismus, the brain ignores the unfocused eye. The strong eye develops normal vision, and the weaker eye becomes amblyopic.
Cloudiness in One Eye
If one eye is cloudy (as a result of cataract or other disorder), that eye fails to focus a clear image for relay to the brain. Again, the brain ignores the bad eye. The good eye develops normal vision, and the cloudy eye becomes amblyopic.
How is amblyopia diagnosed?
Without an eye exam, amblyopia is often difficult to detect, except in obvious cases of strabismus. Therefore, every child should have his/her vision checked by the time he/she reaches the age of four.
Consult a healthcare provider regarding the need for earlier eye examinations if a child has a family history of:
- Childhood Cataracts
- Other Eye Disease
To check vision in babies and young children, we examine the ability of one eye to follow an object, while the other eye is covered. If a baby has amblyopia, and the good eye is covered, he/she may:
- Try to remove or Look Around the eye covering
- Poor vision in one eye is not always a symptom of amblyopia. Amblyopia refers specifically to a developmental disorder of vision. Any diagnosis of amblyopia should include careful examination of the eye itself to rule out other possible causes of poor vision.
How is amblyopia treated?
Treatment of amblyopia involves both correction of the underlying cause, as well as strengthening of the weak (amblyopic) eye.
Treatment of the underlying cause may require:
- Surgery to correct strabismus
- Glasses to correct unequal focusing
- Surgery to remove cataracts
Correcting the cause alone will not cure amblyopia. If amblyopia itself is not treated, potential complications include:
- Severe and permanent loss of vision in the amblyopic eye
- Loss of depth perception
To treat amblyopia, it is necessary to force the weak eye to work. Forcing the weak eye to take control of vision can help improve communication between the weak eye and the brain. Methods to force the weak eye to work include:
- Patching (covering) the strong eye for hours at a time over a period of weeks or months.
- Part-time patching may be continued for years to maintain vision in the weaker eye.
- Blurring vision in the good eye using eye drops or lenses.
How well does treatment work?
If amblyopia is detected early, treatment can improve vision in most cases. On the other other hand, if amblyopia is not detected during early childhood, successful treatment is less likely.