Eye gaze systems provide a means of computer access for individuals who do not have use of their hands, feet or head. Simply by focusing their gaze on keys displayed on a computer monitor, users can browse the Internet, access augmentative communication systems, type, and use environmental controls.
LC Technologies, Inc. (www.eyegaze.com), which markets the Eyegaze Edge, uses a pupil-center/corneal-reflection method of determining where the user is looking. They offer the following explanation of how this wireless system works:
An infrared-sensitive video camera, mounted beneath the System’s screen, takes 60 pictures per second of the user’s eye. A low power, infrared light emitting diode (LED), mounted in the center of the camera’s lens illuminates the eye. The LED reflects a small bit of light off the surface of the eye’s cornea. The light also shines through the pupil and reflects off of the retina, the back surface of the eye, and causes the pupil to appear white. The bright-pupil effect enhances the camera’s image of the pupil so the system’s image processing functions can locate the center of the pupil. The Edge calculates the person’s gazepoint, i.e., the coordinates of where he is looking on the screen, based on the relative positions of the pupil center and corneal reflection within the video image of the eye. Typically the Eyegaze Edge predicts the gazepoint with an average accuracy of a quarter inch or better.