The eye’s reflex to blink has been proven to be sensitive to many neurological issues, like traumatic brain injury, Parkinson’s disease and Huntington’s disease. This suggests that blinking could be a useful tool for neurological assessment.
Although electromyography (EMG)-derived time metrics were used to analyze the blink reflex as early as 1950, quantitative assessment of the blink response was not adopted widely in clinical practice. This is partly because the technology was cumbersome and uncomfortable for the doctor and the patient.
Additionally, EMG is highly sensitive technology that requires strict ambient parameters and was not easily performed outside of a healthcare setting. This limits the applications of the blink reflex as a diagnostic indicator of neurological health. New advances in video and computer technology — including improved digital image capture, higher frame speeds and higher processing speeds — have created a portable, noninvasive, quantitative assessment of blink.
The Blink Reflexometer, a portable device that was developed by the Zucker Institute for Applied Neurosciences at the Medical University of South Carolina. The device has been licensed to BLINKtbi (Charleston, South Carolina). It uses high-speed video to capture and quantitatively analyze a series of blinks that are stimulated by puffs of air. The device then analyzes the recorded blinks based on data acquired from decades of blink reflex research in order to determine if the patient has experienced neurological insult.
The researchers conducted a study with using the Blink Reflexometer on 10 healthy college students and then compared those results to results obtained with EMG. Three parameters were measured in this study: latency (the time between stimulus to first eyelid movement), differential latency (the difference in start time between eyelids) and the duration (the time from start of eyelid movement to when the eyelid opens).
Latency and duration measurements obtained with the Blink Reflexometer were in line with previous results. The only differential latency fell outside of published ranges. The findings suggested that the Blink Reflexometer can provide quantitative measurements of the blink that are in part with the results obtained through an EMG.
"We are excited to be able to take something that had been qualitative and make it quantitative and objective," said lead author Nancey Trevanian Tsai, M.D. "We talk about metrics all the time in medicine but when you are actually able to provide quantitative, objective data, it's a game changer. It's analogous to the difference between saying someone is feverish to measuring the patient's temperature, an objective measurement, with a thermometer."
The study was based on a small number of young, healthy patients. This means larger studies in participants that better represent the general populace will be needed. More studies will be required to verify the usefulness of the blink reflex and of the novel device for neurological assessment in each area of clinical need. Even though the Blink Reflexometer can measure changes in the blink reflex, it doesn’t provide information on the causes of those changes.
If the findings of these studies are promising, the device could make it possible to include the blink reflex as a metric or vital sign in a medical examination. Because it is portable, it could be taken into the field for on-site neurological assessments. Potential uses are the field-side assessment of athletes for concussion or field sobriety tests for marijuana intoxication.
The paper on this research was published in the journal IEEE Journal of Translational Engineering in Health and Medicine.