Guided Progression Analysis (GPA)
Humphrey Field Analyzer II-
i
series User Manual 2660021145640 A
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Introduction to GPA
Guided Progression Analysis (GPA) is a software package for the Humphrey Field Analyzer that is
designed to help practitioners identify and quantify statistically significant progressive visual field
loss in glaucoma patients. The software is designed for use with SITA Standard, SITA Fast and Full
Threshold exams, but not SITA-SWAP exams.
The analysis highlights any changes from baseline that r
epresent larger than expected clinical
variability, and it provides simple plain-language messages whenever changes show consistent and
statistically significant loss. GPA adjusts for ocular media effects in order to help the practitioner
differentiate between the localized losses typical of glaucoma and overall depressions caused, for
example, by progressive cataract.
GPA is based on knowledge that was gained through extensive multi-cen
ter clinical trials in North
America, Europe, and Asia. The plain-language analysis is based on the criteria used in the Early
Manifest Glaucoma Trial (EMGT). GPA incorporates the Visual Field Index (VFI), a new summary
measurement of a patient's visual field status, expressed as a percent of a normal age-adjusted
visual field. The VFI regression analysis is based on recent work by Bengtsson and Heijl.
4
GPA Adds Value to Your Practice
The GPA analysis provides value because it:
• Simplifies and standardizes analysis for change in glaucomatous visual field
s.
• Provides both trend analysis and event analysis in one report.
• Is based upon visual field testing experience g
ained in multi-center clinical trials.
• Provides simple plain-language messages whenever chang
es show consistent and statistically
significant loss.
• Adjusts for cataract and other
media effects.
• Easily applies to a series of visual fields already stored in HFA II-
i
instruments.
• Streamlines workflow and improves clinical confidence.
Event Analysis
GPA provides event analysis with the Progression Analysis
Plot. This plot is based on significance
limits for test-retest variability in Pattern Deviation at each point in the central visual field. The
Pattern Deviation measurement technique is designed to filter out most changes in the general
height of the hill of vision helping to differentiate between localized glaucoma damage and other
sources of vision degradation, such as changes in pupil size or developing cataracts.
Trend Analysis
GPA provides trend analysis with the VFI regression analysis. The
VFI is based only on points that are
significantly depressed in Pattern Deviation, is thus relatively insensitive to visual field changes due
to cataract, and therefore a more robust metric for assessing progression. The VFI values are plotted
to quantify the Rate of Progression (ROP) and provide a visual trend of the progression pattern.
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