A researcher at Stanford has created an alternative to the mouse that allows a person using a computer to click links, highlight text, and scroll simply by looking at the screen and tapping a key on the keyboard. By using standard eye-tracking hardware--a specialized computer screen with a high-definition camera and infrared lights--Manu Kumar, a doctoral student who works with computer-science professor Terry Winograd, has developed a novel user interface that is easy to operate.

"Eye-tracking technology was developed for disabled users," Kumar explains, "but the work that we're doing here is trying to get it to a point where it becomes more useful for able-bodied users." He says that nondisabled users tend to have a higher standard for easy-to-use interfaces, and previously, eye-tracking technology that disabled people use hasn't appealed to them.

At the heart of Kumar's technology is software called EyePoint that works with standard eye-tracking hardware. The software uses an approach that requires that a person look at a Web link, for instance, and hold a "hot key" on the keyboard (usually found on the number pad on the right) as she is looking. The area of the screen that's being looked at becomes magnified. Then, the person pinpoints her focus within the magnified region and releases the hot key, effectively clicking through to the link.

Kumar's approach could take eye-tracking user interfaces in the right direction. Instead of designing a common type of gaze-based interface that is controlled completely by the eyes--for instance, a system in which a user gazes at a given link, then blinks in order to click through--he has involved the hand, which makes the interaction more natural. "He's got the right idea to let the eye augment the hand," says Robert Jacob, professor of computer science at Tufts University, in Medford, MA.

Rudimentary eye-tracking technology dates back to the early 1900s. Using photographic film, researchers captured reflected light from subjects' eyes and used the information to study how people read and look at pictures. But today's technology involves a high-resolution camera and a series of infrared light-emitting diodes. This hardware is embedded into the bezel of expensive monitors; the one Kumar uses cost $25,000. The camera picks up the movement of the pupil and the reflection of the infrared light off the cornea, which is used as a reference point because it doesn't move.

Even the best eye tracker isn't perfect, however. "The eye is not really very stable," says Kumar. Even when a person is fixated on a point, the pupil jitters. So he wrote an algorithm that allows the computer to smooth out the eye jitters in real time. The rest of the research, says Kumar, involves studying how people look at a screen and figuring out a way to build an interface that "does not overload the visual channel." In other words, he wanted to make its use feel natural to the user.

One of the important features of the interface, says Kumar, is that it works without a person needing to control a cursor. Unlike the mouse-based system in ubiquitous use today, EyePoint provides no feedback on where a person is looking. Previous studies have shown that it is distracting to a person when she is aware of her gaze because she consciously tries to control its location. In the usability studies that Kumar conducted, he found that people's performance dropped when he implemented a blue dot that followed their eyes.