Zeiss Humphrey II-i series, Руководство пользователя

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Guided Progression Analysis (GPA)
Humphrey Field Analyzer II-
i
series User Manual 2660021145640 A
8-10
Understanding GPA Reports
GPA reports (GPA Summary, SFA-GPA, Full GPA and GPA Last 3 Follow-up) provide information in
addition to the familiar Graytone Plot, Pattern Deviation Plot, and key indices such as VFI, MD and
PSD. They also provide information that is unique to GPA, including the Deviation From Baseline
Plot, the Progression Analysis Probability Plot (commonly referred to as the “GPA Triangle Plot”), the
GPA Alert and the VFI Plot (with VFI Bar). These features are described below.
Deviation from Baseline Plot
The Deviation from Baseline Plot compares the pattern deviation of the Follow-up test to the
average of the pattern deviation values of the two Baseline tests, and indicates changes at each
tested point, in dB notation. For example, a value of -6 means that the tested point was 6 dB lower
than the pattern deviation value for the same point in the Baseline. A zero (0) means there was no
change from Baseline.
Progression Analysis Probability Plot
The Progression Analysis Probability Plot gives the statistical significance of the decibel changes
shown in the Deviation from Baseline Plot. It compares the changes between the Baseline and
Follow-up exams to the inter-test variability typical of stable glaucoma patients and then shows a
plot of point locations which have statistically changed.
• A single, solid dot indicates a point not changing by a statistically significant amount.
• A small open triangle identifies a degree of deterioration expected less than 5% of the time
at that location in stable glaucoma patients; that is, deterioration at the 5% level (p < 0.05).
Since we are measuring at the 5% level, an average of 2 to 3 triangles can be expected by
chance (out of the 76 stimuli in a 30-2 exam) in any given comparison of a Follow-up exam to
the Baseline exams. While it is important to follow these points, scattered open triangles are
not uncommon in stable glaucoma patients.
• A half-filled triangle indicates statistically significant deterioration at that point in two
consecutive tests.
• A solid triangle indicates statistically significant deterioration at that point in three
consecutive tests.
• An
X
signifies that the data at that point was out of range for analysis. For data that is out of
range, GPA cannot determine whether or not the encountered deviation at that point is
statistically significant. This occurs mainly with field defects that were already quite deep at
Baseline, such that even the maximum available stimulus brightness is within the range of
normal variability, but can also occur when the measured threshold is
higher
than the
Baseline.