Computer scientists have devised a method of "typing" without a keyboard using clever software that creates words and sentences using eye movements alone.
Two Cambridge University researchers have shown that their invention does not result in eye-strain, is just as fast as conventional typing and results in fewer mistakes.
David Ward and David MacKay, physicists in the university's Cavendish Laboratory, are making the software freely available in the hope that computer firms will use the idea, which promises to revolutionise technology for the disabled.
In a study published today in the journal Nature, the scientists say that the system, which monitors the gaze of the user's eye to type up to 34 words a minute, is faster and more reliable than similar "on-screen" keyboards that rely on eye movements.
The software works by following the eye with a tracker and camera as it runs along a list of letters arranged in alphabetical order on the screen. When the eye fixes on a letter, the computer offers a series of intelligent choices about what the next letter should be.
Dr Ward and Dr MacKay say that it is like choosing a desired piece of text from an enormous library of books on a shelf. Instead of choosing each letter in turn, writing becomes like a navigational task.
"The software works like a video game in which the user steers even deeper into an enormous library. A language model is used to shape this library in such a way that it's quick and easy to select probable sequences of characters, and hard to make spelling mistakes," Dr MacKay said.
To write "hello", the user first gazes on the letter "h" and automatically finds a series of further choices beginning "ha", "hb", "hc and so on. The user enters "he" and the computer offers up the next most likely option, including "hel".
Tests showed that the software, called Dasher, worked so well because it relied on the natural ability of the human brain and eye to make continuous pointing gestures, Dr MacKay said. The language model in the software adapts to a person's writing style so that sometimes several words can be written with a glance.
The researchers are forfeiting patenting rights to Dasher, which can be downloaded free from: www.inference.phy.cam.ac.uk/dasher/