Zeiss HUMPHREY 720i, User Manual

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TEST PARAMETERS AND STRATEGIES 4-7
REV. B 02/03 PN 51680-1 HUMPHREY FIELD ANALYZER
II -
i series
Figure 4.2: The Threshold Parameter Setup Screen
Table 4.2: Threshold Test Parameters
(Standard parameter settings appear in bold print )
Threshold Parameter Description
Parameters Settings
Test Strategy SITA Standard ™ This is the standard testing strategy for the Swedish
Interactive Thresholding Algorithm (SITA).
SITA Standard cuts testing time in half relative to the
Full Threshold strategy without compromising test
reproducibility. See Appendix G for more details.
SITA Fast ™ This is a faster version of SITA. SITA Fast cuts testing
time in half relative to the FastPac testing strategy
without compromising test reproducibility. See Ap-
pendix G for more details.
Full Threshold A “bracketing” technique is used to threshold
each test point. An initial stimulus is presented at a
level the patient is expected to see. If seen, the
stimulus intensity is decreased in 4 decibel steps
(0.4 log units) until the patient no longer sees the
stimulus; if not seen, it is increased in 4 dB steps
until seen. The instrument then changes direction,
moving in 2 dB steps until a change in patient re-
sponse is made. The last stimulus seen by the pa-
tient is recognized as the threshold for that point.
The bracketing process described above begins with
4 primary points whose threshold values are deter-
mined at the beginning of the test. The results at
these points then influence the starting levels for
neighboring points in the pattern.
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