Zeiss Humphrey II-i series, User Manual

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Humphrey Field Analyzer II-
i
series User Manual 2660021145640 A
STATPAC Analysis & Printing 7-3
Threshold Test Printout Formats
Until this chapter, this User Manual has focused on the use and operation of the HFA II- i . In
attempting to explain the information provided on printouts, however, we must enter the realm of
interpretation of field results.
Reliability Indices
Humphrey Field Analyzer printouts include reliability indices to help you determine the reliability of
the patient’s responses in interpreting test results. These indices include fixation losses, false
positive errors, and false negative errors. Gaze Tracking can also be used for reliability information.
The HFA II-
i
prints “XX” after scores that fall outside the reliability limits used in the normative
database. In addition, STATPAC printouts include the message, “Low Test Reliability” with excessive
fixation losses and “Excessive High False Positives” when the false positive limit has been exceeded.
Fixation losses are printed as a ratio, such as “3/10”. The first number represents the number of
errors committed, while the second number represents the number of times the instrument checked
for each of these errors. Limits for SITA Standard and SITA Fast are 20% for fixation losses and 15%
for false positive errors. There is no limit displayed for false negative errors with SITA testing.
Clinical results having poor reliability, but for which the STATPAC analysis is normal, may well be
normal. Results showing poor reliability and for which the STATPAC analysis is outside normal limits
require careful analysis. Utilize the Gaze Tracking graph to help determine how steady patient
fixation was during the length of the test.
If the only “XX” on a test result applies to fixation losses and you are sure the patient was fixating
well, the problem may have been poor blind spot positioning rather than poor patient reliability.
High false negative response rates are commonly seen in abnormal fields produced by completely
reliable patients. On the other hand, test results may be unreliable at false positive rates lower than
the level required to generate the “XX” symbol.
Note: Many patients are more relaxed and better test takers when performing visual fields during a
second office visit. This leads to more reliable results, because the patient has a better idea of the
task and the time it will take to complete the visual field test. Therefore, repeat testing is
recommended for all first-time visual field patients. This is known as the “Learning Effect.”
Foveal Threshold
If you used the foveal threshold option when the test was run, the HFA II-
i
will print the measured
value just below the test duration. When the patient’s foveal threshold is depressed significantly

(p < 5%), a probability symbol will appear next to the value shown. This symbol is identical to those
used for the probability plots and indicates the deviation from age normal. See the following
discussions on Total and Pattern deviations for details.