2001 Conference Proceedings

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Eye Tracking Technology: A Comparative Study

Barbara Phillips, MS OTR ATP
Occupational Therapist bphillips@dhs.co.la.ca.us 
Las Floristas Center For Applied Rehabilitation Technology
at Rancho Los Amigos National Rehabilitation

Bruce Fleming, BSME ATP
Rehabilitation Engineer btfleming@dhs.co.la.ca.us 
Las Floristas Center For Applied Rehabilitation Technology
at Rancho Los Amigos National Rehabilitation

Andy Lin, BS
Assistive Technology Specialist alin@dhs.co.la.ca.us 
Las Floristas Center For Applied Rehabilitation Technology
at Rancho Los Amigos National Rehabilitation

Background

In 1998, the Las Floristas Center for Applied Rehabilitation Technology (CART) at Rancho Los Amigos National Rehabilitation Center and the ALS Association (ALSA) of Los Angeles County formed a collaborative relationship in which clients with ALS are evaluated by CART to meet their assistive technology needs. Augmentative Communication (AAC) devices from the ALSA loaner library are available for long-term loan. Clients are followed from the initial contact through the rest of their lives. As their disease progresses, it is common to make adaptations to their AAC and computer access methods to support their independence. As muscles grow weaker, they may ultimately be able to function with only one switch site. Often, that same site can be utilized for a longer period of time by changing the type of switch they are using. It is common to use the same site for a light-touch mechanical, then ultimately a zero-force light sensing switch.

When switch sites are no longer available, or when the realization that this will be a possibility, the client or family may look toward eye tracking technology for communication and/or computer access. To date, there are four different eye-tracking technologies on the market. Two use cameras mounted on or near a computer monitor and two types use a camera mounted on glasses or headgear that the user wears. Each system has valuable features and specific limitations. Ultimately, the needs and skills of the user will determine the appropriate system to serve their purposes.

State of the Art Technologies

The Eyegaze Communication System, by LC Technologies, Inc., uses a video camera, mounted below a monitor, and a video processing system to observe one of the user’s eyes as it navigates the display. Nothing is attached to the user’s head or body. This computer-based product operates as a stand-alone communication, writing, reading and ECU system, and can be connected to a second computer to function as a keyboard and mouse emulator. The Quick Glance, by EyeTech Digital, also uses a camera mounted on the monitor to track eye movement and software to translate it into mouse movement. In contrast to the stand-alone, multi-purpose Eyegaze system (above) the Quick Glance operates as mouse emulator directly on a Windows-based computer based system.

The ion, from Eye Control Technologies, uses a headset that incorporates two cameras in the visor above the eyes to track eye gaze and monitor eye blinks for click/selections on a computer display.

The Vision Key, by H.K. EyeCan Ltd., uses a key chart placed in a viewer mounted on a pair of eye glass frames and operates as a stand-alone communication system, and can attach to a computer to perform keyboard and mouse emulation.

Functional and Technological Limitations

Although an eye-control system may appear as an option when all other controls have failed, there is some evidence that the loss of ocular motor control, often found in later stages of diseases such as ALS, can adversely affect the ability to use it.

The Study

A study using subjects with normal ocular motor control is being conducted to compare eye-tracking systems and their features. One of the considerations is user position. For example, if the person needs to be in a reclined position, then he will be more able to use a system that is worn on his face. If the person is able to sit upright and maintain his head in an upright position without deviation, use of one of the systems with monitor-mounted camera may be more appropriate.

This study was prompted by a number of motivators:
  1. An increasing number of inquires from new and on-going clients.

  2. Our professional needs to become familiar with the technology in order to better serve our clientele.

  3. The apparent lack of previous eye-tracking system comparisons and limited expert knowledge in the Assistive Technology professional field.
Several different tasks are evaluated in respect to the control of the mouse emulator and the different tasks that need to be accomplished. Our evaluators are performing a battery of tasks to evaluate each eye-tracking system’s characteristics, including

To evaluate systems in these performance areas, this study is using a variety of tools including

Discussion/implications

Relatively few individuals use eye tracking access systems. For those that do, it is often the only access method that will work. Reasons for this limited use include the high cost of systems and the extensive set up and support required for success. The populations who might be appropriate include those with Muscular Dystrophy, high-level Spinal Injury, and Amyotrophic Lateral Sclerosis (ALS). Of particular concern is the ALS population, which many vendors target with this technology.

Recent clinical evidence suggests that in the end stages of the disease, full range of eye motion may be impaired (Pamowski and Jost, 1995). Full range of eye motion is recommended for eye-gaze access methods. With some eye tracking systems, there tends to be greater success if the individual can still blink well enough to perform the “click” function rather than using the dwell to select. Further clinical research regarding the changes in ocular motor control is needed. Rest breaks are recommended for individuals using eye gaze as an access to technology, as well as for their primary communication methods which also includes low tech solutions. The eye muscles, like other muscles, fatigue with use and require rest to support optimal function.

It will be interesting to study individuals with ocular motor involvement to determine the ease of adapting or modifying the software for optimal performance.

About CART

The Las Floristas Center For Applied Rehabilitation Technology at Rancho Los Amigos National Rehabilitation Center has been serving persons with disabilities of all ages for over 10 years in the greater Los Angeles, California, USA area. Assistive Technology teams address needs for seating and wheeled mobility, augmentative and alternative communication, computer access, and environmental control. For more information, call CART at (562) 401-6800, or visit our website at http://www.rancho.org/cart 

References

Palmowski A , Jost WH, Osterhage J,Kasmann B, Schimrigk K, Ruprecht KW. Eye movement in amyotrophic lateral sclerosis: A longitudinal study. German Journal of Opthalmology, 1995 Nov, 4(6), 355-62.


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