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-5
The Glaucoma Change Probability Analysis Printout
The Glaucoma Change Probability Analysis (GCP) is only available when you use the Full Threshold
strategy. This analysis is based on visual field change, using the derived total deviation values. The
newer Guided Progression Analysis (GPA) uses pattern deviation values and works with the SITA test
strategies. Both the Glaucoma Change Probability Analysis and GPA are designed to facilitate
interpretation of Central 30-2 and 24-2 threshold test results for patients with suspect or manifest
glaucoma. These two methods of interpretation are intended to allow maximum use of available
test results. Both of these analyses are particularly useful for determining change over time. That is
to say, they are effective in discriminating random variation from true change. For further discussion
of GPA, please refer to
Chapter (8), "Guided Progression Analysis (GPA)."
The Glaucoma Change Probability Analysis works from Baseline data for the individual patient to
create change probability maps and to calculate significance limits for measured changes in mean
deviation. Because the global indices (MD, SF, PSD, and CPSD) are not necessarily sensitive to
important localized changes, the Glaucoma Change Probability Analysis offers point-by-point
significance limits. This allows analysis of smaller areas of the visual field defect and enables early
detection of change.
The Glaucoma Change Probability plots identify those locations in the visual field which have
changed by more than what would be expected simply due to normal variability. The significance
limits for this analysis were obtained by testing a large group of glaucoma patients four times in the
course of a month. Normal variability in these patients was found to depend on the depth of the
original defect at Baseline, the location in the visual field, and the overall Mean Deviation of the
visual field. Points changing from Baseline by more than the empirical significance limits are
highlighted with small triangles.
In general, the Glaucoma Change Probability Analysis will use the average of the first two selected
tests as a Baseline and all subsequent tests as Follow-up. There are two exceptions:
1. If only two tests are selected, the first will be used as the Baseline and the second as
Follow-up.
2. If the mean deviation of the first test falls significantly below the regression line of those of the
other tests (p < 5%), and five or more tests are to be analyzed, STATPAC will discard the first
test, use the second and third tests to calculate the patient’s Baseline, and analyze the
subsequent tests as Follow-up tests.
Note: Baseline tests should be representative of the actual Baseline status of the patient. Baselines
established from tests in which the patient was obviously inattentive, inexperienced, or too eager to
press the response button can lead to false positive or false negative conclusions upon Follow-up.
Create a new pair of Baseline tests if significant change has occurred (cataract surgery, for
example).
The Glaucoma Change Probability Analysis was designed to allow comparison of a series of
Follow-up tests with the Baseline findings in order to detect and confirm changes in the visual field.
Prudence requires that changes detected in one Follow-up test be confirmed in at least one
additional test before medical therapy is changed significantly or surgery is ordered.