Zeiss Humphrey II-i series, Руководство пользователя

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Humphrey Field Analyzer II-
i
series User Manual 2660021145640 A
Reference to Older Test Strategies L-1
(L) Reference to Older Test Strategies
Introduction
The SITA Standard and SITA Fast testing strategies have replaced the Full Threshold and FastPac
testing strategies for most threshold testing. In addition, SITA-SWAP is replacing the Full Threshold
and FastPac strategies for testing SWAP visual fields due to the much shorter test times available
when utilizing SITA-SWAP. These pages add additional details for the Full Threshold and FastPac
testing strategies in case you need to use these strategies for any reason. Again, it is recommended
you use either SITA Standard or SITA Fast whenever possible.
Variations in Reliability Indices
For Full Threshold and FastPac tests, false positive errors, false negative errors, and fixation losses
are all printed as a ratio. The false positive and false negative results will appear as a fraction (
i.e.,
Total number of false positive errors divided by the total number of trials). If false positive or false
negative errors equal or exceed 33% of the trials, the characters “XX” will appear both on the
screen and on the printout, although test reliability may be compromised at false positive rates that
are much lower than 33%.
The visual fields used in developing STATPAC for the Full Threshold and FastPac strategies were
those of subjects whose reliability indices were within certain limits. Test results showing fixation
loss scores of 20% or more and false positive or false negative errors of 33% or more were excluded
as unreliable. The significance limits thus derived were more restrictive than they would have been
had unreliable test results not been excluded.
Fluctuation Values (Full Threshold and FastPac Only)
The fluctuation value, also referred to as short-term fluctuation (SF), is an option that you can use
with the Full Threshold and FastPac strategies. Fluctuation is not displayed when using either of the
SITA strategies. When fluctuation is turned on, the threshold is measured twice at 10 pre-selected
points. The HFA II-
i
then calculates a fluctuation value on the basis of the differences between the
first and second measurements at each of the 10 points. This value is an index of how reliable a
patient’s responses were during the test.
A patient who is very consistent will have a low fluctuation value, while a patient whose responses
vary significantly will have a high value. All fluctuation values that lie significantly outside the
normal limits will be flagged on the printout with p values,
e.g. p < 0.01.
The fluctuation option will add about 10% to the test time. When test results are analyzed with
STATPAC, the fluctuation value is used in the calculation of CPSD, one of the four global indices. If
the fluctuation is turned off, the CPSD will not be calculated.
A high fluctuation value may be the first sign of glaucomatous field loss in patients who are
otherwise reliable subjects. It is also associated with established field loss in reliable subjects. On
the other hand, a high fluctuation value may indicate simply that the patient was inattentive or did
not understand the test.