In recent decades, many advances have been made to help people who have lost function of their limbs, but the latest is one of the most significant yet.
The new technology, which has been outlined in a paper published in Current Biology, might allow people who have almost completely lost the ability to move their arms or legs to communicate freely, by using their eyes to write in cursive.
The eye-writing device tricks the neuromuscular machinery into doing something that is usually impossible - voluntarily producing smooth eye movements in an arbitrary direction.
Lead researcher Jean Lorenceau from Université Pierre et Marie Curie-Paris, said the advance could be of great benefit for people deprived of limb movements, such as those with Lou Gehrig's disease (also known as ALS).
"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," he explained.
According to the expert, it may also help to improve eye movement control in people with certain conditions such as dyslexia or ADHD, and assist professionals such as athletes or surgeons, whose activities strongly rely on eye movements.
Dr Lorenceau explained that in everyday life, smooth pursuit eye movement is used to track moving targets, but it is normally impossible to control those movements smoothly in any direction.
The technology relies on changes in contrast to trick the eyes into the perception of motion, so when viewing a changing visual display, people can learn to control their eye movements smoothly and at will, without much practice.
"One can also imagine that, in the long term, eye movements can routinely be used in man-machine interactions," said Dr Lorenceau, who is now working on a better version of his eye writer, with tests with ALS patients.