Amblyopia, often called "lazy eye", is when one eye develops good vision while the other does not, the eye with the poorer vision is called amblyopic. Usually, only one eye is affected by amblyopia, but it is possible for both eyes to be "lazy." This condition is called bilateral amblyopia.
Amblyopia is common; approximately two or three out of every 100 people has amblyopia. The best time to correct amblyopia is during infancy or early childhood.
If amblyopia treatment is not begun as early as possible, several problems can develop that can seriously affect vision from childhood into adulthood:
- The amblyopic eye may develop a serious and permanent visual defect
- Depth perception (seeing in three dimensions) may be lost, because good vision in both eyes is needed
- If the stronger eye becomes diseased or injured, it can mean a lifetime of poor vision
- People with amblyopia in one eye are more than twice as likely to lose vision in the healthy eye from trauma
Amblyopia is detected by finding a difference in vision between the two eyes or poor vision in both eyes. Poor vision in one eye does not always mean that a child has amblyopia.
It is not easy to recognize amblyopia in children. A child may not be aware of having one stronger eye and one weaker eye. Unless the child has an eye that is misaligned or another condition that can be seen, there is often no way for parents to tell that something is wrong.
Symptoms of an amblyopic eye sometimes include:
- Poor vision in one eye or overall poor vision
- Squinting, tilting the head or closing one eye to see
- Poor depth perception (difficulty judging relative distances between objects)
- An inward- or outward-wandering eye
Amblyopia is caused by any condition that affects normal use of the eyes and visual development. Amblyopia has three major causes: strabismus, unequal focus and refractive errors, and cloudiness in the eye tissue.
Strabismus (misaligned eyes):
Amblyopia occurs most commonly with strabismus, which is misaligned or crossed eyes. The crossed eye "turns off" to avoid double vision, and the child uses only the better eye. The misaligned eye then fails to develop good vision. Click here for more information on strabismus.
Unequal focus and refractive errors:
Refractive errors are eye conditions that are corrected by wearing eyeglasses or contact lenses. Amblyopia occurs when one eye is out of focus because it is more nearsighted, farsighted, or astigmatic than the other. If one eye is out of focus, this unfocused (blurred) eye "turns off" and becomes amblyopic. The eyes can look normal, but one eye has poor vision. This is the most difficult type of amblyopia to detect since the child appears to have normal vision when both eyes are open. Amblyopia can also occur in both eyes if both eyes have very blurred vision. This can happen when there is a high degree of nearsightedness, farsightedness, or astigmatism.
Cloudiness in the normally clear eye tissues:
An eye disease such as a cataract may lead to amblyopia. Any factor that prevents a clear image from being focused on the retina at the back of the eye can lead to the development of amblyopia in a child. This is often the most severe form of amblyopia.
Lazy eye correction or treatment should begin as soon as possible so that the child's visual system can develop properly.
If refractive amblyopia is a problem, eyeglasses may be prescribed first to correct the focusing errors. If glasses alone do not improve a child's vision, then patching is needed — usually for weeks to months. Covering the child's stronger eye with a patch forces the child to use their weak eye. Another way to accomplish this technique is to blur the vision in the strong eye with special eyedrops or a pair of glasses with a blurry lens over the stronger eye. Even after vision has been restored in the weaker eye, it may be necessary to continue patching the lazy eye part-time for a few more years to maintain the improvement.
Amblyopia is usually treated before surgery to correct misaligned or crossed eyes, and patching or blurring with eyedrops is often continued after surgery as well.
If the doctor finds a cataract or other problem in the eye that is causing the visual problem, surgery may be required to correct the problem causing amblyopia.