Elektron Technology HENSON 8000, User Manual

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40 Henson Perimeter User Manual
© 2017 Elektron Technology
3. 2
Zat a t hreshold t est
ZATA (Zippy Adaptive Threshold Algorithm) is a new threshold program that is
faster and more accurate than earlier threshold tests (Full Threshold, Fast
Threshold). Shorter test times are important in perimetry, as patients find it
hard to maintain their attention much beyond three minutes and loss of
attention is associated w ith increased variability.
When possible the ZATA program uses the data from a previous visual field
result to seed starting values. When no prior data is available it starts from
age-dependent normal values. Starting from prior threshold estimates not only
makes the test faster but also improves the accuracy of the threshold
estimates.
The ZATA test can use either the 30-2, 24-2 or 10-2 pattern of test stimuli.
ZATA Fa s t a n d ZATA St a n d a rd . ZATA Fast differs from ZATA Standard in that
it has looser terminating criteria. The terminating criteria dictate how accurate
the threshold estimate must be before the program stops testing each location.
Looser terminating criteria mean that the ZATA Fast test w ill be quicker than
ZATA Standard, although the accuracy of each threshold estimate w ill be
reduced by a small amount. ZATA Fast is appropriate for patients w here less
accurate estimates are acceptable. i.e. those w ith no established loss.
The ZATA program presents one stimulus at a time and the patient responds to
each seen presentation by pressing a
response button.
At the end of the test the results can be view ed in a variety of different
w ays.
The standard printout includes, threshold values (numeric and gray scale),
defect values (age and pattern related), probability values (age and pattern
related) along w ith a series of global indices (MD, PSD, Hemifield), test details
and patient demographics.
To g e t mo re h e lp o n a te s t s cre e n ite m click o ve r th e ite m in th e ima g e b e lo w .
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