Eye Tracking: Eye-Gaze Technology

Fig. 23.1
Tobii EyeMobile on Windows 8 Pro tablet supported in an upright position on Daessy C-shaped desktop stand. © 2012 Daedalus Technologies, Inc. Tobii Gaze Selection interface is displayed on the right side of the screen, which in conjunction with Tobii’s Windows 8 Functions Overlay, gives users a hands-free access to Windows 8 apps through the eye-gaze technology. © 2013 Tobii Technology. (Photo: Judy Lariviere)

Literate adults use the eye-gaze technology to access an onscreen keyboard for written communication, email, and social networking. When using an onscreen keyboard, it is often used in conjunction with word prediction and abbreviation expansion so that a user does not need to spell full words that he or she is typing.

Eye-gaze technology can also be used to access other software applications that are available on a computer-based AAC device including web browsers for researching information or accessing online services such as banking or shopping, for reading digital books, magazines, or news articles, and for entertainment purposes such as watching movies, listening to music, or playing games.


This chapter focuses on how eye-gaze technology is used to help people with disabilities access an AAC device, also known as a speech-generating device (SGD), to support face-to-face and written communication, and increased independence (Fager et al. 2012; Tobii Assistive Technology 2012; Tobii Technology 2010).

How eye-gaze technology works as an access interface. Eye-tracking systems use infrared technology in a remote eye-gaze accessory that is connected a computer. Invisible, but safe levels, of infrared light illuminate the user’s eyes and create reflections off the surface of the eye. Cameras in the remote eye-gaze accessory capture the image of the reflection of the light off the cornea and pupil (Tobii Technology 2010). Complex mathematical computations are performed by the computer to determine the direction of the gaze on the computer screen; in other words, the location or button at which the user is looking or fixing their gaze. As soon as the mouse pointer moves to this location of the screen, selection of the specific item/button containing a symbol/picture, word(s), letter, individual selections, or activations are made in one of three ways: (a) dwelling or maintaining gaze or visual attention on a location for a preset length of time, or (b) by blinking, or (c) through activation of an external switch that essentially performs a mouse click (Fager et al. 2012; Tobii Technology 2010).

Most eye-gaze systems have communication software that integrate a “snap-to-grid” feature that works by automatically moving the mouse pointer to the center of the nearest item or button on the screen where a person’s eye gaze is detected. This represents an easier motor pattern, especially for children learning to use an eye-gaze system for communication, in comparison to the level of skill and accuracy required for controlling the mouse or cursor movements in an open Windows environment through mouse emulation or recently developed gaze interaction techniques .


Candidates for the Intervention

Eye-gaze technology is becoming more widely used and is suitable for children and adults with various disabilities, including the following:

  • Severe physical disabilities and developmental disabilities (Fleming et al. 2010)

  • Autism (Norbury et al. 2009)

  • Motor disabilities (Chin et al. 2008; Najafi et al. 2008),

    • Amytrophic lateral sclerosis (ALS; known as Lou Gehrig’s disease/motor neuron disease; Ball et al. 2010);

    • Cerebral palsy

    • Stroke/aphasia (Wallace and Bradshaw 2011)

    • Spinal cord injury (Boatman 2013) ;

    • Other individuals with CCN who rely on eye movements for access to an AAC device (Fager et al. 2012) including Rett syndrome (RTT; Baptista et al. 2006; Didden et al. 2010).

Little information is currently available about the selection criteria for prescribing eye-gaze technology across all of these diagnostic groups.


Assessment of the ability to benefit from using eye-gaze technology as an access method for SGD or a computer can take place in a variety of settings, including a hospital, clinic, home, work, and/or educational settings. When an individual has access to their own eye-gaze system, he/she may use it at home, school, work, and other settings in the community.

The Role of the Occupational Therapist

Prescription of eye-gaze technology, in the USA, is most frequently based on its use with SGDs or AAC devices for face-to-face communication. Funding of SGDs is often approached from a medical standpoint and dependent upon a detailed report from a speech-language pathologist (SLP) and a letter of medical necessity from a physician. This documentation must demonstrate that using a SGD with an eye-gaze accessory enables an individual to independently communicate his/her needs to caregivers across various environments.

With the application of eye-gaze technology to populations with more complex access needs, a thorough assessment process will depend upon the participation of a multidisciplinary team including the client, parent(s), family members, SLPs, occupational therapists (OTs), teachers, and other members of the educational team, physicians, and in some cases, opthamologists. The OT’s role is to participate in assessments regarding an individual’s access to and selection of an AAC device, computer, or tablet by providing information about the individual’s physical abilities with respect to:

  • The position(s) in which he or she will access the eye-gaze system and the positioning of the eye-gaze system in relation to the user’s eyes across these positions; natural head and body movements in these positions and how these may impact use of an eye-gaze system. This information would assist in determining which eye-gaze systems to include in a trial based on the dimensions of the system’s track box. This track box represents an invisible area in front of the eye-tracking cameras within which the user’s eyes and head can move and continue to be tracked or have eye fixations captured.

  • The individuals’ natural range of eye movements and pattern of gaze (i.e., tendency to look up or down), visual tracking with one or both eyes in relation to items presented on a computer screen, field of vision, and length of natural gaze or visual fixation and/or ability to make a controlled blink are important for identification of the selection technique with an eye-gaze system.

  • Sensitivity to contrast of colors or inability to shift gaze away from specific colors.

  • The individual’s previous experience in using other access interfaces and why these met with limited success. It is important to document that the user has tried and used other access methods such as a switch(s), joystick, optical head pointer, and how these affected his/her ability to use an AAC device to communicate.

This information supports the multidisciplinary team in reviewing the features of available eye-gaze systems and identifying the eye-gaze systems that would provide the best match to the individual’s physical, cognitive, and literate profile and for inclusion in eye-gaze trials.


Applications of Eye-Gaze Technology

The assessment process takes place over multiple sessions and a trial period of 2 weeks to 1 month, depending upon the age and disability of the client and the application of eye-gaze technology for communication with software or for windows control. It is recommended that users be evaluated using at least two different eye-gaze systems as each eye-gaze system functions differently.

The clinical assessment process consists of the following:


Identifying the locations and positions in which the individual will use the eye-gaze system.



Positioning the eye-gaze system in relation to the individual’s eyes. The system’s Track Status Window is retrieved and shown on the computer display to assist with positioning the user’s eyes vertically and horizontally in relation to the eye-gaze accessory (Fig. 23.2). An indicator in the Track Status Window or camera view shows when the computer or AAC device with the eye-gaze accessory has the optimal working distance from the user’s eyes. Whenever the user or computer/AAC device is repositioned, it is important to display the Track Status Window to ensure that user’s eyes are positioned for optimal access and use. Positioning the user’s eyes in relation to the Track Status Window is often confused with the calibration procedure, which is completed the first time an individual uses the eye-gaze system .


Fig. 23.2
Track Status Window on Tobii I-12. © 2013 Tobii Technology. The white dots show the position of the user’s eyes in relation to the eye-gaze accessory or cameras. The white arrow in the middle green portion of the vertical bar on the right side of the Track Status Window indicates that the device is positioned at a suitable distance from the user’s eyes. (Photo of the screenshot: Judy Lariviere)



Initiating the calibration process after an individual’s eyes are located in the Track Status Window. During the calibration procedure, an individual needs to look at and maintain his/her gaze on specific points on the screen while multiple images of the eyes are taken. The calculated distances of the gaze from the calibration points are represented by lines extending outside the calibration area. After calibration has been completed, the results of the process are displayed (Tobii Technology 2010; Figs. 23.3 and 23.4). In cases where a poor calibration is obtained (Fig. 23.4), an individual’s parent or sibling can calibrate the system for them as their eyes represent a close genetic match. This strategy ensures the individual is using the eye-gaze system with a high-quality calibration .


Fig. 23.3
Calibration result of a successful 9-point calibration on a Tobii I-12. © 2013 Tobii Technology. The markings in the center of the circles indicate that the individual fixed and held his/her gaze on the presented visual stimulus during the calibration process. (Photo of screenshot: Judy Lariviere)


Fig. 23.4
Calibration result of a 9-point calibration on a Tobii I-12 where the user has shifted gaze from the points during the process.© 2013 Tobii Technology. Although the Tobii I-12 reports the calibration as successful, it is suggested that the calibration results may need to be improved through again or improving one or more points individually. This screenshot shows that bottom middle gaze point for the left eye needs to be calibrated as the left eye’s fixation on this point was not registered during the calibration process. (Photo of screenshot: Judy Lariviere)



The communication-based software that will be used on the AAC device will often be determined by the individual’s SLP based on his/her assessment of the communication and language abilities dependent on the individual’s age, literacy skills, communication skills, symbol, and onset of their disability.



Determining the mounting system(s) to be used. A mounting system refers to the structure that supports or secures the eye-gaze system in space, often in an upright or vertical plane, in relation to the position(s) of the user’s eyes and head during use of the system. There are various types of mounting systems available for positioning the eye-gaze system for when a user is sitting in a wheelchair or at a desk or table in a classroom, lying down in bed, or standing at a table.

The mounting system will be used to support the eye-gaze system, often in an upright position, in various locations at home, school, work, and in community. Sometimes, users need two different mounting systems to ensure they have access to eye-gaze technology in different positions and settings. For example, a wheelchair mount will meet the need for accessing the device when the user is sitting in their wheelchair but another mount is necessary when he/she is lying down, etc. A rolling floor mount may meet the needs for when a user is at home but a table mount may be more suitable for when sitting at a desk in school.



Trial period. Then, the individual borrows or rents the device so he or she gains experience in using it to interact with their communication partners in the settings where it will be used.



Integrating the technology into the client’s activities of daily life (ADL). The usefulness of eye-tracking technology is dependent upon the OT’s knowledge about human factors and ergonomic design. For example, positioning of the client’s eyes and the eye-gaze module, the track box and screen sizes, in relation to his/her eyes, tolerance for head and body movements the software used for communication, and representative symbol sets. OTs can also contribute valuable input to the design and layout of the pages on a screen based on their evaluation of an individual’s natural eye-gaze patterns and range of eye movements in horizontal, vertical, and diagonal directions .



Recording eye gaze patterns. Clinicians can use Tobii Gaze Viewer software (​www.​tobii.​com/​en/​assistive-technology/​north-america/​products/​software/​tobii-gaze-viewer/​) to record and view an individual’s gaze patterns when he or she is using any application with a Tobii eye tracking accessory. The data can be saved as an image(s) or a movie(s) for playback. The tracking data provides information in the form of heat maps (showing where a user has focused his/her visual attention) and gaze plots (showing the order in which a user has looked at different locations or images/buttons on a screen). Tobii Gaze Viewer gives OTs an assessment tool that provides objective measures for evaluating an individual’s access to different areas of the screen, as well as various sizes and layouts of pictures/buttons, using an eye gaze systemhttp://www.​tobii.​com/​LearningCurve.


Evidence-Based Practice

General. Most of evidence-based research examines eye tracking and patterns of gaze rather than the users’ actual use of eye-gaze technology for communication and other ADL activities. Until now, users’ use and emotional experiences of using eye-gaze technology are documented by “stories” like Steve Gleason’s (Microsoft 2014). Additional testimonials from people who experience greater independence, access to social networks, return to work, and enjoy artistic expression are available on the Tobii technology homepage ​www.​tobii.​com/​en/​assistive-technology/​global/​user-stories/​. Therefore, scientific RTC studies are required.

Evidence-based clinical practice from the author’s clinical experiences. An eye-gaze trial page set for girls and women with Rett syndrome that has been programmed in Tobii Communicator (Figs. 23.5, 23.6 and 23.7) for use on Tobii eye-gaze systems (© Lariviere 2009–2014). This page set has been used in more than 200 eye-gaze trials with girls and women with Rett Syndrome while they attend their clinic appointments at Katie’s Clinic for Rett Syndrome (UCSF Benioff Children’s Hospital Oakland, USA).

The trial page set was specifically designed for girls with Rett syndrome based on their natural eye movements from left to right across a page and ease in looking either up or down (Lariviere 2011; Figs. 23.5, 23.6 and 23.7).

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May 21, 2017 | Posted by in GENERAL | Comments Off on Eye Tracking: Eye-Gaze Technology
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