Screening for glaucoma progression by using non‐parametric tests

Abstract

PurposeAutomated perimetry still represents the gold standard in long term glaucoma monitoring.Early detection of progression tendency in glaucoma patients is crucial. Purpose of this study was to assess an alternative fast and convenient method compared to GPA (Humphrey Perimeter, Carl Zeiss®) for detecting glaucoma progression shortly after diagnosis‐24 months.MethodsWe studied in a longitudinal manner 41 eyes from 41 patients with early open angle glaucoma forms, followed in the first 24 months after diagnosis. Glaucoma was defined according to EGS criteria and a minimum of 5 valid visual fields were required form each patient. All specific glaucoma clinical data were recorded and progression was verified by two distinctive methods: Glaucoma Progression Analysis (GPA) software from Hymphrey Visual Field Analyzer and a non parametric analysis (NPA) according to Wesselink protocol.ResultsIn GPA analysis, a positive „event” (progression) was detected in 11/ 41 eyes, 26.82%. NPA confirmed progression in all GPA cases, but additionally detected 8 moreprogression cases (46.34% eyes). The concordance between tests was good (k = 0.596, p = 0.000), with positive correlation (Mc Nemar test r = 0.652, p = 0.008). In the first 2 years after diagnosis, GPA sensitivity was 26.82% and a specificity of 73.33%, whereas NPA sensitivity was 46.34% and comparable specificity 72.41% to GPA. Likelihood ratio for progression (LR) in GPA was 1.00 vs 1.51 for NPA analysis.ConclusionsNPA tends to overestimate progressor number in a cohort, but its purpose is to allert and orient the clinician on the progression profile of the followed patients. In the first years, the GPA analysis can be highly inaccurate, therefore combining two methods with similar specificity might aid this purpose and ease the glaucoma care management.