Elektron Technology HENSON 8000, User Manual, Page: 42 / 159

42 Henson Perimeter User Manual
© 2017 Elektron Technology
3 .2 .1
Blin d s p o t
At the beginning of a ZATA test the Henson 8000 searches for the eye's blind
spot.
It starts off by presenting a Supra-Threshold stimulus at the most likely location
of the blind spot. If this is not seen, this location is stored as the blind spot. If it
is seen then a stimulus is presented at the next most likely location. This is
repeated until either the patient does not see one of the stimuli or until all the
potential blind spot locations have been tested.
The blind spot location is used throughout the test as a check of fixation. Every
now and again a stimulus is presented at the established blind spot location,
and if the patient sees this stimulus (presses the Response button) it is
assumed that they w ere not fixating accurately. The number of blind spot tests
and the number of times the stimulus w as seen in the blind spot are displayed
as fixation losses on the status bar (see below ) and
printout .
In a reliable patient fixation losses should not exceed 20%.
Occasionally, the perimeter may fail to find the patient's blind spot, i.e. the
patient presses the response button for every potential blind spot location.
This is usually the result of a false positive response by the patient (they
pressed the response button in error w hen the stimulus w as presented in their
blind spot).
When this occurs, a message w ill ask if you w ant to repeat the search
(relocate) or to continue w ithout blind spot checks.
Click one of these options to continue testing.
It is possible to repeat a search for the blind spot during the test by clicking
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