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Following your gaze
by Juan C. Dürsteler [message nº 38]

Eye-tracking systems substitute the mouse and keyboard for disabled people and are being already used to test usability.

These type of systems have been present in the market, in a more or less experimental way, for around 20 years. They appeared in vision research laboratories to study visual phenomena, especially the involuntary saccadic movements of the eye that it performs when observing the environment.

With the popularisation of computers, some of these eyetracking systems have led to the substitution of keyboard and mouse for a system that allows the software to know what part of the screen we are looking at and placing the cursor accordingly. Staring at one button can activate it.

The systems devoted to experimentation are typically mounted on a helmet or band attached to the head and carry two miniaturised video cameras that follow the reflected image of an infrared LED on the cornea (Video Oculography). Other systems use eelctrodes that measure the potential of the skin surrounding the eyes (Electro Oculography). Both are quite bothersome for continued use.

More recently non obtrusive systems have appeared that aren't in contact with the user and don't interfere with their field of vision. An example is the model ASL 504 or the QuickGlance system by Eye Tech that includes software that allows the user to lead the cursor of Windows 98 with the gaze. These systems don't suppose any bother to the user as the camera and LEDs are below or at the side of the screen.

The current systems are quite inefficient as mouse and/or keyboard substitutes. Eye movements are partly involuntary and partly voluntary. This makes getting used to leading the cursor with the gaze and maintaining it fixed on one point a lot more complicated than taking a mouse and learning how to use it.

However they can be a very interesting solution for people with disabilities that prevent them from using a mouse or keyboard. Among these systems you can find LC Technologies EyeGaze. These systems stand out especially for the software that allows the user to read and write text, switch the lights on and off, dial telephone numbers or to use a Windows 98 computer using only the gaze. It's particularly appropriate for people that suffer from Multiple Sclerosis, Amyotrophic Lateral Sclerosis (ALS), Cerebral Palsy or Tetraplegia among others.

But a more recent use, although far less evident and that is arising with certain strength is the usability testing of a web page, a multimedia kiosk or a software user interface by using eye tracking. At least two companies are offering such services. One of them is the Dutch company TestUsability B.V.. They use a helmet mounted eye tracking system to detect which zones of a given web page, software interface or multimedia kiosk attract the visual attention of the user and which of them don't. This data along with the recording of the mouse clicks and of the verbal answers or expressions of the user can then be analysed.

Another example is the U.S. company eyetracking.com that performs similar functions. Nevertheless their own web begins with a slow download of a flash presentation that disables the "Back" button of Internet Explorer, making you wonder if their own web has passed their test . 

It's clear that eye tracking alone is insufficient to assess usability and has to be combined with the verbal opinions of the user and the knowledge of which buttons and links he/she has used, among other issues. But it is of great help, since eye tracking allows you to see what parts of the screen are more interesting to the users, even when they don't mention it explicitly. Uninteresting elements (like for example ads) are detected as well.

Eye tracking nowadays offers solutions to some disability problems and helps us in testing the usability of our designs. 

Research in this field goes on just as the miniaturisation of eye tracking systems for wearable computers does too.

Links of this issue:

http://www.a-s-l.com/model504.htm  
http://www.eyetechds.com/  
http://www.lctinc.com/  
http://www.testusability.com/  
http://www.eyetracking.com/  
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