[Paris, France/ Medicine] - A novel device that can track eye movements and translate them into smooth lines on a screen gives people with no limbs or with limb paralysis the ability to write and draw after only a few hours of training. Developed by the Centre de Recherche de l′Institut du Cerveau et de la Moelle Epinière (CNRS/UPMC/Inserm), the device enables users to write numbers, letters, figures and even a signature.
Although the eye can follow a moving object very efficiently, it is not capable of performing smooth, regular movements in front of a static background; it performs instead a series of irregular jerks. This is why current writing devices using eye movements only allow users to choose from words or letters that are displayed on a screen.
Using a visual illusion
To obtain smooth trajectories of the eye, Jean Lorenceau, of CNRS/UPMC/Inserm came up with the idea of using a visual illusion called reverse-phi, which has been known since the 1970s but which has not until now found any applications. The illusion occurs when several hundred disks whose luminance varies over time at a frequency of around 10-15 Hz are displayed on a screen. When the user′s eyes move over this flickering background, the subject has the clear impression that the disks move with the displacement of the eyes.
Since the human eye is capable of following moving objects with precision, the illusory movement of the disks induced by the movement of the eyes gives them a sort of moving support, allowing them to realise regular and non-jerky trajectories. An oculometer records the movements of the user′s eye and very simple software enables these movements to be visualized on a screen. Two to four training sessions lasting around 30 minutes are all that are needed to be able to manage eye movements and draw letters. Well-trained individuals can write with their eyes at more or less the same speed as handwriting.
This device could give persons suffering from limb paralysis the means to personalize their writing, write their own signature and, more generally, to express themselves and communicate in a more creative and free manner. The next step in this research will consist in proposing to persons suffering from amyotrophic lateral sclerosis to use the invention. However, Lorenceau believes that this system opens the way to other applications: it could be used to train pilots, surgeons, sportsmen, artists and other persons whose activities require precise oculomotor control. It could also make it possible to design security systems based on the recognition of eye movements. [hw][Photo: J.Lorenceau – Current Biology (July 2012)]