How paralysed patients could write again - using their eyes
PARALYSED patients could use their eyes to project handwriting onto a screen thanks to new technology which traces the pupils as they "draw" the shapes of letters.
Although our eyes are capable of smoothly tracking moving objects it is usually impossible for us to make such controlled and precise movements at will.
As a result, paralysed patients can currently use eye-reading devices to point towards a particular object on a screen, but are unable to communicate freely by drawing the outlines of letters.
Now a French researcher claims to have discovered a way of "tricking" the brain into thinking it is watching a moving object, allowing the patient enough control to trace letters and numbers.
Jean Lorenceau, of Universite Pierre et Marie Curie-Paris, said: "Contrary to the current belief, we show that one can gain complete, voluntary control over smooth pursuit eye movements.
"The discovery also provides a tool to use smooth pursuit eye movements as a pencil to draw, write, or generate a signature."
The technique relies on an illusion caused by a flickering screen filled with a random array of static discs varying in contrast.
When the eyes are fixed on the screen the discs appear faint and still, but when the patient shifts their gaze the stationary field appears to move with them in the same direction.
A ring of coloured dots also follows the eyes to enhance the effect, duping the brain into thinking the eyes are following the dots.
Lorenceau reported in the Current Biology journal that after three half-hour training sessions healthy volunteers could direct their eyes in any direction, and further training allowed them to write words at a rate of 20-30 characters per minute, similar to cursive handwriting.
He wrote: "After brief training, participants gain volitional control over smooth pursuit eye movements and can generate digits, letters, words, or drawings at will."
Fine-tuning the device will allow tetraplegic patients and people with conditions like motor neurone disease and cerebral palsy to "enjoy a personal and emotionally rich way of communicating with others," Lorenceau concluded.