Eye opener for brain-damaged patients

"Locked in" patients with brain damage that has left them mute and motionless may be able to communicate with a system that measures the size of their pupils, a new study has found.

Individuals suffering from locked-in syndrome have lost motor control, but remain aware and alert. The rare condition usually results when damage occurs to the brain stem, which controls motor function. Stroke, traumatic brain injury and amyotrophic lateral sclerosis (also known as Lou Gehrig's disease) can cause locked-in syndrome.

Many patients with locked-in syndrome communicate with an alphabet chart, blinking to indicate their choices as a caretaker points to a letter. Others use devices that measure eye movement patterns representing "yes" or "no".

Locked-in patients who cannot move their eyes at will may be able to use systems that translate brain activity into speech, but these often require surgical implantation and special training.

A new system called the EyeSeeCam measures changes in pupil size that happen involuntarily - even in people unable to blink - and decodes them into "yes" or "no" responses, potentially offering an easier alternative for such patients, including completely locked-in individuals.

In the 1960s, researchers discovered that pupil size can be used to measure mental effort. The bigger a person's pupils, the harder his or her brain is working. Neuroscientists used these findings to develop the EyeSeeCam, which takes advantage of how people's pupils dilate when they try to solve maths problems.

Since this happens automatically, patients did not need to be trained to use the EyeSeeCam, said Wolfgang Einhauser, a neurophysicist at Philipp University of Marburg in Germany, who helped develop the device.