(CNN) -- How many times have you seen a young child with a patch over one eye or wearing glasses with one lens blocked and wondered why? Chances are that child has something called amblyopia (sometimes called "lazy eye"), where one eye is not being used by the brain because it doesn't see as well.
After looking at more than 10 years of data, researchers now say children as young as a year old can be reliably screened for amblyopia; by using a camera that takes pictures of the eye, symptoms of the condition can be detected long before it becomes apparent, according to a study published Monday in the journal Pediatrics.
The goal is to identify children with this problem as early as possible, says lead study author Dr. Susannah Longmuir, "so we can start treatment before they have a problem or treat it before it gets worse."
She says very young children can already be developing amblyopia, but they do not know they have a vision problem because it's all they know - and they appear to parents to have normal vision. But as they get older, the problem gets worse.
One eye could be out of focus, or the eyes aren't straight and the brain doesn't want to see double, so it turns off the bad eye, says Dr. Daniel Neely, chairman of the vision screening committee for the American Association for Pediatric Ophthalmology and Strabismus (AAPOS), who was not involved in the research.
The brain then gets used to not using the eye, he says. But the brain can be re-taught how to use the eye that's just not doing enough -- if caught early. That's where the patches, glasses or eye drops come in. By covering the good eye up or putting eye drops in to make the vision in the good eye blurry, the brain is forced to used the other eye.
"We know that after age 5, the effectiveness of the treatment is diminished," Neely adds. "The problem is most vision screenings happen when kids go to school," he says - close to when the window of correction closes.
"Current U.S. Preventive Services Task Force (USPSTF) guidelines, issued in January 2011, only recommend testing children for this eye condition between the ages of 3 and 5, citing insufficient evidence to recommend testing younger children.
Researchers at the University of Iowa designed a study to help the USPSTF by providing the necessary evidence to include toddlers in their recommendations, says Longmuir.
"We wanted to see if we could reliably screen the younger children (1 to 3 year olds) just as well as the 3-5 year olds," says Wanda Pfeifer, who is not only a co-author of the study but also a orthoptist (vision therapist) who works with Longmuir.
Volunteers across the state were trained "to conduct free vision screening events with the MIT PhotoScreener," according to the study. This is a special purpose camera that takes pictures of the eye - which look a lot like the unflattering "red-eye" in family photos. It measures the optic of the eye and looks for risk factors for amblyopia.
One of the strengths of the study is that everybody used the same device. Longmuir says screenings were typically done at daycare centers where they could easily find the primary age group they were targeting - 6 months to 4 years of age - but no child was turned away.
She says 210,695 screenings of children's eyes were conducted from May 2000 to April 2011. The youngest children were 6 months old, the oldest were 7 to 8 years old. The average age was 3.4 years.
The researchers found no statistically significant differences in the reliability of photoscreens in the 1- to 2-year-old age group compared with that in the 3- to 5-year-old children.
"If you are a year old, the test is going to be as reliable as if they (the children) are 3 years old," says Pfeifer, who read all of the thousands of screens.
Get your child screened as early as age 1 because if your child is developing amblyopia, his or her vision could be corrected. "By 7 or 8, your vision is locked in," says Longmuir.
Neely says if your child fails a screening, then it's time for a full eye exam. Parents and pediatricians need to be aware of the benefits of this screening. If your child hasn't been screened, parents should request it, says Longmuir.
Just last week AAPOS revised its guidelines to include screening for children as young as 1.
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