'Locked-in' coma patients communicate through eye pupil size changes

Patients otherwise unable to communicate can answer yes or no questions through a simple system that measures the size of their pupils, European scientists say. The simple system of a laptop and a camera, requiring no specialized equipment or training, takes advantage of changes in pupil size that naturally occur when people do mental arithmetic, researchers report in the journal Current Biology. In addition to helping those who are severely motor-impaired to communicate, the system might also be extended to assessing the mental state of patients whose state of consciousness is unclear, the researchers say. "It is remarkable that a physiological system as simple as the pupil has such a rich repertoire of responses that it can be used for a task as complex as communication," Wolfgang Einhauser of Philipps-Universitat Marburg in Germany said. In an experiment, healthy people were asked to solve a math problem only when the correct answer to a yes or no question was displayed on a screen. The mental load associated with solving that problem caused an automatic increase in pupil size, researchers said, which could be measured and translated into an accurate answer to questions such as, "Are you 20 years old?" The researchers then tested their pupil response algorithm on seven "typical" locked-in patients who had suffered brain damage following a stroke, and in many cases were able to discern an answer based on pupil size alone. That could make an important difference for those who need it most, the researchers said. "For patients with altered state of consciousness -- those who are in a coma or other unresponsive state -- any communication is a big step forward," Einhauser said.