One by one, 24 children sat at a desk in Georgina Lynch’s lab on the Spokane campus of Washington State University. Using a specialized camera that takes hundreds of pictures per second, Lynch and her colleagues measured how long it took the children’s pupils to adjust when she waved a penlight in front of their eyes.
Among those with autism, it tended to take longer than normal.
The study, conducted earlier this year, bolsters a growing body of research that suggests the pupils of children with autism constrict more slowly when exposed to flashes of light than those of their typically developing peers. Although the experiment was relatively small, it suggests that a simple penlight-response test – the kind routinely performed in doctor’s offices – may one day help diagnose autism and prompt treatment earlier in a child’s life.
The results were so promising that Lynch, an assistant clinical professor in WSU’s department of speech and hearing sciences, now plans to conduct a larger, more detailed experiment.
“The use of eye-tracking in autism has emerged in the last decade,” she said. “Basically, as the technology has advanced, it’s allowed us to ask new questions.”
Lynch and her colleagues, Drs. Stephen James and Nancy Potter, tested 24 children ages 10-17. Half of the children had autism and half did not. Using the high-speed camera and eye-tracking software, the researchers measured pupil responses in each eye over four seconds in four trials. They found the pupils of children in the autism group took markedly longer to constrict in 70 percent of the trials.
“This is innovative research, and it’s using the technology in a way that’s just a little bit different than it’s been used in the past,” Lynch said. “It helps us get a picture of exactly when that stimulus was presented and how long it took the pupil to respond.”
Lynch suspects there may be a link between the social deficits associated with autism and a sort of misfiring in the optic and oculomotor nerves in the brainstem. Abnormalities in those nerves could help explain why people with autism have difficulty making eye contact and are often sensitive to bright light, she said. Without the ability to pay attention to other people’s facial expressions during conversation, someone with autism may become asocial or socially awkward.
Lynch’s study is unique in that it focused on a purely physiological response – that is, pupils constricting to let in less light. In contrast, most previous studies have focused on behavioral responses such as averting one’s eyes or gazing in another direction.
“Earlier studies have looked at how people look at things and study their environment,” said Dr. Steve Edelson, director of the Autism Research Institute, a nonprofit based in San Diego. “There have been reports about vision (in relation to autism) for 50, 60 years. But as far as using it to make a diagnosis, that’s new and unique.”
Lynch was careful not to overstate the implications of her research. She said the penlight test, no matter how reliable, wouldn’t replace the behavioral and developmental screenings currently used to diagnose autism. But it may prompt parents and doctors to look for symptoms earlier in a child’s life.
According to the Centers of Disease Control, diagnosing autism can be difficult because “there is no medical test, like a blood test, to diagnose the disorder.” Instead, doctors rely on interviews with parents and close – yet sometimes “subjective” – observations of a child’s behavior and intellectual development, Lynch said.
Some are diagnosed as young as 18 months, but most don’t receive a final diagnosis until years later because they don’t display all the features of autism, or those features are missed in screenings. The average age of diagnosis in the United States is 4, meaning many children with the disorder don’t receive proper therapy by the time they enroll in school.
“There’s hundreds of researchers around the world looking for what we call ‘biomarkers’ to help diagnose autism in the womb and soon after they’re born,” Edelson said. Suspected biomarkers for autism include visible brain abnormalities, cell activity and specific antibodies in the mother’s womb, he said.
Although there is some debate within the scientific community, autism is commonly considered to exist on a spectrum with varying degrees and permutations of symptoms, rather than categorized into discrete subgroups. In Lynch’s study, the children in the autism group had no intellectual or language impairments, no unrelated vision or hearing impairments and took no prescribed medications.
The pilot study was funded by the university and presented at the International Meeting for Autism Research in May in Salt Lake City. To see if their findings hold up, the researchers plan to conduct more trials in clinics and doctor’s offices beginning sometime next year; those trials will examine children younger than 10 as well as a broader range of autism symptoms.
“It’s obvious that they’re going to have to differentiate between different kinds of autism and other disorders, mental health disorders,” Edelson said. “So the question is: With pupil size, can you generalize it to all autism?”
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