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7-12 STATPAC ANALYSIS & PRINTING RESULTS
REV. B 02/03 PN 51680-1 HUMPHREY FIELD ANALYZER II -
i
series
In cases where the patient is suffering from a cataract, the visual field is depressed more or
less evenly. The only change from test to test and from the normal box plot is a general
depression over time. Therefore, the shape of the box plot remains fairly normal, but the
whole symbol is moved downward on the graph.
A visual field with a deep scotoma covering a small number of points will result in a box plot in
which the box is more or less normal and there is a long tail. When a scotoma deepens over
time, the length of the tail increases.
If the scotoma enlarges to involve more than 15% of the points tested, the lower limit of the
box will be further depressed, and depending on the extent and gravity of the field loss, the
boxes may be very elongated.
The box plot section of the Change Analysis printout gives the dates of the tests included in the
analyses. Change Analysis is available for the 24-2 and 30-2, as well as combinations of 24-2
and 30-2 tests, but not for the 10-2 pattern. If 24-2 and 30-2 tests are mixed in the Change
Analysis printout, global indices are calculated only on the 24-2 portion of the 30-2 test
results.
Change analysis The lower half of the Change Analysis printout displays summaries of the global indices MD
summary of global indices (Mean Deviation), PSD (Pattern Standard Deviation), SF (Short-term Fluctuation), and
CPSD (Corrected Pattern Standard Deviation) for the tests shown in the box plot.
The summary results are presented chronologically and in the same order as in the box plots.
Thus, test dates may be taken from the box plot.
To facilitate interpretation, the p < 5% and p < 1% limits for the normal population are shown
as dashed reference lines. If, for example, the symbol indicating a test appears above the 5%
line, the index value on the test is not significant at the 5% level. If it falls below the 5% line,
the index value is significant at the 5% level. Similarly, if the symbol falls below the 1% line, the
index value is significant at the 1% level; that is, less than 1% of the normal population has an
index value as large as or larger than that found in the test.
Linear regression If five or more fields are analyzed on a Change Analysis printout, and all test results to be
analyzed were run with the same strategy, STATPAC will automatically perform a linear regres-
sion analysis of mean deviation (MD). One of two messages, MD SLOPE NOT SIGNIFICANT or
MD SLOPE SIGNIFICANT, will be printed below the MD plot when a linear regression analysis
has been performed. The calculated slope of MD in decibels per year and a tolerance for that
slope, expressed as a p value, will also be printed.
A “significant” message means that it is likely that mean deviation has changed in the direction
of the estimated slope, and the lower the “p” value, the more likely it is. However, it remains
for the clinician to establish whether this indication on the test results is caused by progressive
field loss or by other factors.
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