Eye-opening biomarkers for autism and ADHD discovered

The eyes may be able to signal neurodevelopmental disorders such as autism spectrum disorder (ASD) and attention deficit hyperactivity disorder (ADHD), according to new research from Flinders University and the University of South Australia (UniSA).

Working with McGill University, University College London and the Great Ormond Street Hospital for Children, the researchers found that recordings from the retina could identify distinct signals for both ADHD and ASD, providing a potential biomarker for each condition.

ADHD is a neurodevelopmental condition characterised by being overly active, struggling to pay attention, and having difficulty controlling impulsive behaviours. ASD is also a neurodevelopmental condition where children behave, communicate, interact and learn in ways that are different from most other people. According to the World Health Organization, one in 100 children has ASD, with 5–8% of children diagnosed with ADHD.

“ASD and ADHD are the most common neurodevelopmental disorders diagnosed in childhood. But as they often share similar traits, making diagnoses for both conditions can be lengthy and complicated,” said Flinders research optometrist Dr Paul Constable.

“Our research aims to improve this. By exploring how signals in the retina react to light stimuli, we hope to develop more accurate and earlier diagnoses for different neurodevelopmental conditions.”

Using the ‘electroretinogram’ (ERG) — a diagnostic test that measures the electrical activity of the retina in response to a light stimulus — the researchers found that children with ADHD showed higher overall ERG energy, whereas children with ASD showed less ERG energy. Constable said the preliminary findings, published in the journal Frontiers in Neuroscience, indicate promising results for improved diagnoses and treatments in the future.

“Retinal signals have specific nerves that generate them, so if we can identify these differences and localise them to specific pathways that use different chemical signals that are also used in the brain, then we can show distinct differences for children with ADHD and ASD and potentially other neurodevelopmental conditions,” he said.

Indeed, this isn’t the first time the eyes have provided a potential biomarker for a neurological condition, with Australian and Canadian researchers last year finding that a combination of a type of atypical, twitching eye movement called ‘square wave jerks’, together with anxiety, is a promising two-element biomarker for anorexia nervosa.

“Ultimately, we’re looking at how the eyes can help us understand the brain,” concluded UniSA’s Dr Fernando Marmolejo-Ramos, a co-researcher on the new study.

“While further research is needed to establish abnormalities in retinal signals that are specific to these and other neurodevelopmental disorders, what we’ve observed so far shows that we are on the precipice of something amazing.”

Image credit: ©stock.adobe.com/au/irena_geo

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