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:
- An increasing number of inquires from new and on-going
clients.
- Our professional needs to become familiar with the technology
in order to better serve our clientele.
- 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
- Precision
- Reliability
- Latency
- Complexity (of setup, and normal operation)
- General Ease-of Use
To evaluate systems in these performance areas, this study is
using a variety of tools including
- Mouse Maze, a mouse tracking game to address precision and
smoothness of movement.
- Solitaire, to address click and drag functions.
- Moving files, to address acquiring and targeting.
- On-Screen keyboard to address precision
- Editing text to address a combination of all the tasks.
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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