Eye Tracking

Even in cases of severe physical disability, eye movement is often preserved.  Thus, a person who cannot move any limb may be able to "look at" objects of interest.  

Eye-gaze interface products fall into three primary categories:

• Add-on devices, generally in the form of a camera bar that is mounted on the device screen. The cameras provide high resolution images of the user's eyes, so that the position of the pupil can be determined, often through infrared reflection from the user's retina. These devices provide sufficient resolution, often with two cameras working together, to position the mouse pointer over a desired target on the screen.
• Add-on cameras for eye-gaze are often as expensive as the device they are being connected to.  If the device already has a built-in (or add-on) webcam, it may be possible to provide sufficient control through that camera.  Specialized eye-gaze software performs image analysis to track eye-gaze without the need for specialized cameras.  Often, this is combined with expanded controls to compensate for the lower precision of mouse pointer control.
• Some devices are designed to be used by people with severe disabilites, so have eye-gaze built-in.  Some of these devices provide full standard computer control, while others are designed for very specific tasks.