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Serious buffeting that may occur when
flying at high speed and low altitude can create visual blurring,
hindering a pilot's ability to fly safely. NASA-funded research
into the muscular physiology of eye vibration was the impetus
for an optical instrument, now in medical use, that accurately
measures eye movements.
Starting as far back as 1965, NASA's Ames Research Center
contracted with the Stanford Research Institute (SRI) International
of Menlo Park, California, to model the human visual-accommodation
system, starting directly with the retinal image. This research
was directed at how the major muscle systems control the human
visual system.
Although a considerable amount of experimental information
had been gathered regarding each of these systems, there was
scant understanding of how control was actually achieved. One
question that had gone unanswered was the voluntary and involuntary
aspects of the human eye
| The Eyetracker,
built by Fourward Optical Technologies, can precisely monitor
eye movements, benefiting the medical field in various ways,
from neurological diagnosis to blood flow monitoring. |
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Several years of incremental NASA funding helped foster SRI-built
eyetracking devices. These tools were able to anticipate, track,
and monitor involuntary ocular movement horizontally, vertically,
and with respect to depth of field. This development did not
go unnoticed by leading academic and research institutions as
an important instrument for understanding the visual system.
Since 1988, Fourward Optical Technologies, Inc., of San Marcos,
Texas, has been manufacturing and marketing the Dual-Purkinje-Image
(DPI) Eyetracker under an exclusive license. Purkinje images
are four reflections produced from the front and rear surfaces
of the cornea and lens. By observing the movement of the first
and fourth Purkinje images with the DPI Eyetracker, the direction
of gaze over a large, two-dimensional visual field can be determined
with great accuracy. The instrument operates with infrared light,
requires no attachments to the eye, and is not disruptive to
normal vision.
Since its introduction by SRI, the Eyetracker has gone through
several generations of development. The price of the early device
was cut by more than half, making it suitable for clinical medical
use. Applications of the Eyetracker are impressive. In cases
of ocular bleeding, lasers can be used to stem the flow. The
Eyetracker makes it possible to accurately target these problem
areas, increasing the accuracy and the effectiveness of the treatment.
Also, various brain disorders can now be diagnosed, as the Eyetracker
can zero-out the eye's involuntary movements during diagnosis.
Working in concert with lasers, the Eyetracker can assist non-invasive
determination of a patient's circulatory health. By accounting
for the eye's natural involuntary movements, the Eyetracker enables
the operator to monitor blood flow by accurately targeting the
retinal capillaries for Doppler blood flow studies.
The Eyetracker has a pointing accuracy on the order of one
minute of arc and a response time on the order of one millisecond.
By attaching Fourward Optical Technologies' Infrared Optometer
to the device, continuous measurement of eye focus is possible,
producing a 3-D Eyetracker. Eyetracker units are installed in
over 11 countries around the globe, in addition to 30 or more
sites in the United States.
Current and potential applications of the Fourward Optical
Technologies' DPI Eyetracker include analysis of visual perception,
mapping retinal features, neurological investigation, drug evaluation,
and even the analysis of advertising material. No doubt the company
has an eye toward the future.
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