Most parents have heard the term "lazy eye" but might not know that it refers to a common eye condition in children called amblyopia. "Amblyopia is poor vision in an eye that is otherwise normal," says David L. Rogers, M.D., clinical assistant professor of ophthalmology at The Ohio State University, director of research in the department of ophthalmology at Nationwide Children's Hospital in Columbus, Ohio, and a member of the American Association for Pediatric Ophthalmology and Strabismus (AAPOS). "In other words, the eye is healthy but it just doesn't see well."
Amblyopia affects two to three percent of people and it's the most common cause of visual impairment in kids. In fact, it's so common that it's responsible for more vision loss in children than all other causes combined, says the AAPOS. Here's what happens: In order to have normal vision, our eyes and brain need to work together properly. When one eye doesn't see well for some reason (more on that later), the brain begins to favor the stronger eye and essentially ignore images coming in from the weaker eye. Over time, vision in the weaker eye can become permanently lost.What Causes It?
There are three main causes of amblyopia, says Dr. Rogers. One cause is strabismus, or misalignment of the eyes. This condition can be visible as an eye that "wanders" or turns in, out, up, or down. When an eye isn't straight, it essentially gets turned off and doesn't develop good vision. Another type is anisometropic, or refractive, amblyopia, which occurs when one eye has a different prescription than the other. For example, one eye may be more nearsighted or farsighted than the other. Typically, the brain will rely on the eye with better vision and ignore the other eye. The third major cause is an eye disease such as a cataract, which causes cloudy vision in the affected eye or a condition such as ptosis (a droopy eyelid). Again, the brain will favor the stronger eye and ignore the weaker one. In this case, the one with the cataract or droopy eyelid.How Can You Tell If Your Child Has It?
One of the tricky things about amblyopia is that there may not be any outward signs that a child has it. "Unless amblyopia is associated with misalignment of the eyes--a wandering eye is visible, for example--or a droopy eyelid, it may not be noticeable at all," says Dr. Rogers. "Most children with poor vision in one or even both eyes may act normal. To children, the way they see is normal so if they see things blurry, they assume everyone else does, too." For this reason, amblyopia is usually discovered through the vision screenings that are done at routine pediatrician checkups and/or in school. If your pediatrician or school nurse detects a problem during a screening, your child will be referred to an ophthalmologist for a comprehensive eye exam. Parents should also bring their child to the eye doctor if they notice that their child has poor vision in one or both eyes, tends to squint, tilt his head, or close one eye to see, is poor at judging distance between objects (depth perception), or complains of headaches, as these could all be signs of amblyopia.How Is It Treated?
Early treatment for amblyopia is key to developing normal vision. According to AAO, the best time to address the condition is during infancy or early childhood. There are two main goals with treatment: One is to treat the issue with the weaker eye. For example, by removing a cataract, surgically correcting a misaligned eye, or prescribing glasses to improve vision in the case of refractive amblyopia. The other is to strengthen the weak eye by forcing the child to use it. This is often accomplished by patching the dominant eye or by blurring vision in the stronger eye (blurring can be done with eye drops or the prescription in eyeglasses). This treatment can take weeks or months, and the earlier your child's amblyopia is addressed, the better her chances are for successful treatment.
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