Do the eyes have it?

Examining the retina may aid in the diagnosis of attention-deficit/hyperactivity disorder (ADHD), new research shows.

Confirming prior work, researchers observed that patients with untreated ADHD have elevated "background noise" on pattern electroretinography (PERG) compared with healthy controls.

They now report that the elevated noise normalizes with treatment for ADHD, with PERG patterns on par with those in healthy controls.

Emanuel Bubl, MD, from the Department of Psychiatry and Psychotherapy, Saarland University in Germany, reported their latest findings here at the American Psychiatric Association (APA) 2016 Annual Meeting.

"There is growing evidence for a special relevance of background noise, or non- stimulus-driven neural activity, in ADHD," Dr Bubl told Medscape Medical News. "Findings from animal studies as well as human research supports this line of thought, and our results directly support findings from basic research, which is intriguing."

PERG — which is akin to electrocardiography (ECG) of the retina — provides an electrophysiologic measurement of the activity of the retinal ganglion cells. "The great strength in investigating the retina is that you are investigating a local network, which you have good access to. We like to compare it to an ECG of the eye," said Dr Bubl.

The researchers used PERG to measure the response of the retina to a checkerboard visual stimuli in 20 patients with ADHD and 20 healthy controls. The patients with ADHD were tested before and after treatment with methylphenidate. 

Neuronal noise before treatment was higher in the ADHD group than the control group and significantly correlated with inattention measured with the Conners' Adult ADHD Rating Scales (CAARS), the researchers found. Treatment with methylphenidate normalized the elevated background noise in the patients with ADHD.

The data support that elevated background noise is associated with ADHD and point to a neural correlate for the disorder, the researchers say.

ADHD medication effectively reduces distractibility and improves attention, and animal studies suggest that a basic mechanism of action is by decreasing neuronal noise or background firing, Dr Bubl explained in his presentation.

"There is great research going on in neural correlates in ADHD, with a focus on alteration in the dopaminergic system in different brain regions," Dr Bubl told Medscape Medical News. "As with other findings, if we get more evidence for an elevated retinal noise in ADHD I think this is a promising tool."

"In ophthalmology," he added, "PERG is a standard diagnostic instrument, which has proven its great value in clinical practice. In psychiatry, it is a research tool at the moment. However, our results support further research to explore the potential as a clinical tool in the future."

Chandra Sripada, MD, PhD, from the Department of Psychiatry at the University of Michigan, Ann Arbor, who wasn't involved in the study, said, "The results do look very interesting [but] the sample size is small," he cautioned. Nonetheless, "I would say [this is] promising work and points to the need for future work in this area," he added.

American Psychiatric Association (APA) 2016 Annual Meeting. SCR-The Broad Interest in Psychiatry, No 2. Presented May 18, 2016.

http://www.medscape.com/viewarticle/863808?src=wnl_mdplsnews_160527_mscpedit_wir&uac=60196BR&impID=1110162&faf=1