Accessible Technology in the 21st Century
|| a stanford sophomore college project ||

.eye tracking.



Tracking an EyeEye tracking is a growing field of alternative computer inputs for the many disabled individuals who have very little mobility except for their eyes. “Traditional” eye tracking technology uses an LED directed to the pupil of the user’s eye, causing a reflection. The angle of this reflection can then be measured and used to determine the location of the eye to move the cursor or pointer on the screen. This requires the user to stare at a particular item for a few seconds in order to select it, but has the benefit of being unobtrusive to the individual (14). ERICA (Eye-gaze Response Interface Computer Aid) is one of the most popular forms of this type of tracking. The interface is a series of boxes; by selecting one, a user will be able to choose from a series of sub-boxes. This can be very time consuming, but is comparatively better than a simple onscreen keyboard. With a keyboard with so many options on the screen, a system that relies on timed responses can create frequent errors from glancing or unintentional, natural movement (15).

Electro-oculography is a relatively new technique that utilizes the small voltage (+.4 to +1 millivolts) of the eye with respect to the retina. By placing electrodes on the skin around the eyes, variations in voltage can be measured that indicate horizontal and vertical movement. Researchers at SUNY – Stony Brook are working on a system where text is selected by a wink rather than a pause. This can be done by monitoring the vertical movement of the eyes; a sharp surge in voltage occurs with either a blink or a wink. By monitoring both eyes, the system can tell the difference between a naturally occurring blink and a non-natural wink, allowing the user more control over their input device (15). This allows for quicker selection of text with less delay and allows the user more freedom of motion to glance or look at other things in between selecting objects or characters.

(14) Cleveland, Nancy. “Eyegaze Human-Computer Interface for People with Disabilities.” First Automation Technology and Human Performance Conference. 7-8 Apr. 1994. LC Technologies, Inc. 18 Sept. 2005 <>.
(15) Shaviv, Bernard. “The Design and Improvement of an Eye Controlled Interface.” Eye Tracking. 19 Sept. 2005 <>