THURSDAY, July 24 (HealthDay News) -- A genetic mutation that causes a congenital eye movement disorder called Duane syndrome has been identified by American and U.K. researchers, who said the finding may improve understanding of how the visual system develops.

People with Duane syndrome, which affects nerve growth in the eye, have limited sideways eye movement. The condition, which is more prevalent in women and in the left eye, affects about half a million people worldwide.

In this study, researchers isolated the genetic mutation from affected families and introduced the mutation into chick embryos, which have a visual system similar to that of humans. The chick embryos developed similar defects in nerve growth.

"By understanding how this gene causes Duane syndrome, we can begin to achieve a wider understanding of how the visual system develops in the womb. This raises the possibility of better diagnosis and even genetic treatments for visual conditions such as Duane syndrome," Dr. John Chilton, an academic fellow in clinical neuroscience and molecular biology at the Peninsula Medical School in the United Kingdom, said in a news release.

"We also discovered that the gene responsible for Duane syndrome is widely expressed throughout the nervous system, so the next question to be answered is why only the nerves that control the eye muscles are affected," Chilton added.

The study was published in the July 25 issue of the journal Science.

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