Elektron Technology HENSON 8000, User Manual, Page: 32 / 159

32 Henson Perimeter User Manual
© 2017 Elektron Technology
3 .1 .3 .1 Sin g le s t imu lu s a lg o rit h m
This algorithm is used to set the single stimulus test intensity w hen the
Threshold Related option is selected.
The threshold sensitivity is measured at four test locations, one in each
quadrant. The locations are displaced 9 degrees from the vertical and
horizontal meridians.
At each location the algorithm starts off 1dB brighter than the expected
threshold for the patient's age. It uses a repetitive bracketing procedure
w ith 1dB steps until six presentations have been made at all four
locations.
The average intensity of the last four presentations, at each of the four
test locations, is then taken as the threshold. To guard against the
inclusion of data from locations w here the threshold is abnormally
depressed, the algorithm excludes data from locations w here the
average of the last four presentations is below the 95% confidence
limits of the expected age setting. If all test locations are excluded, the
threshold is set at 4dB below the age setting.
Ten demonstration presentations are made prior to the collection of
Heart data.
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