A simple test examining involuntary eye movements may provide an objective way to tell whether individuals have attention-deficit/hyperactive disorder (ADHD) and whether stimulant medication will be an effective treatment, new research suggests.
Investigators from Tel Aviv University in Tel Hashomer, Israel, observed increased microsaccades and blink rates in adults with ADHD, which normalized with methylphenidate treatment.
"We had 2 objectives going into this research," lead investigator Moshe Fried, PhD, from the Goldschleger Eye Institute, said in a statement. "The first was to provide a new diagnostic tool for ADHD, and the second was to test whether ADHD medication really works — and we found that it does. It is certainly not a placebo, as some have suggested."
The study was published in the August issue of Vision Research.
"Striking" Predictive Effect
"The rationale behind our study was following recent studies ― of ours and others ― which found that the rate of microsaccades is inversely correlated with the level of attention," Dr. Fried told Medscape Medical News.
In this latest study, the investigators recorded involuntary eye movements in 22 adults with ADHD with and without methylphenidate and 22 control individuals while they performed the test of variables of attention (TOVA).
They found that unmedicated ADHD patients had significantly higher rates of eye blinks and microsaccades compared with control participants. This effect was largest in the peristimulus period, "where eye movements should be suppressed because they could interfere with the task," the researchers write.
In addition, stimulant medication had a "striking effect" on involuntary eye movements, with full normalization of the microsaccade rate to the control level and partial normalization of blink rates, mainly in the peristimulus interval, they report.
"In order to develop a clinical differential diagnostic tool, a more refined study should be conducted," said Dr. Fried. "Specifically, patients should be divided into subtypes ― for example, 'inattentive' vs 'impulsive' ― and also the control group should be screened to exclude potentially undiagnosed ADHD subjects."
"Promising" Diagnostic Tool
"This is an interesting paper," Emanuel Bubl, MD, from Albert-Ludwigs University of Freiburg, Germany, told Medscape Medical News.
"The study has many strengths, starting with an easy approach to the patient by investigating the visual system and documenting a normalization after therapy," Dr. Bubl commented.
"The results are in line with findings from animal research and human studies where methylphenidate acts by stabilizing neuronal networks and reducing background noise. The authors link their finding to the arousal system, and there is good evidence that especially the dopamine system with the dopamine-1 receptor plays a prominent role in ADHD," he added.
"In my opinion, a diagnostic strategy, accessing the eye to find a diagnostic tool, has a lot of potential to reach clinic and is a promising tool for the future," Dr. Bubl said.
In his own research, Dr. Bubl has found that examining the retina may aid in the diagnosis of ADHD. As reported by Medscape Medidcal News, in a small study, he and his colleagues showed that patients with ADHD displayed significantly elevated "background noise" on pattern electroretinography compared with their healthy peers.
The study was supported by the National Institute for Psychobiology in Israel, the Charles E. Smith family, and the Israel Science Foundation. The authors report no relevant financial relationships.
Vision Res. 2014;101:62-72. Abstract
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Cite this: Eye Test May Diagnose ADHD, Predict Treatment Response - Medscape - Aug 20, 2014.