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M. Ng, L. Racette, J. P. Pascual, L. M. Zangwill, C. A. Girkin, J. M. Liebmann, R. N. Weinreb, P. A. Sample; Comparison of Visual Field Severity Classification in Eyes With Glaucoma. Invest. Ophthalmol. Vis. Sci. 2009;50(13):5286.
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© ARVO (1962-2015); The Authors (2016-present)
To compare recently developed severity classification systems applied to a large number of Standard Automated Perimetry fields.
The study included 2,085 eyes (49% OD) from 1,214 participants from the Diagnostic Innovations in Glaucoma Study (DIGS) and the African Descent and Evaluation Study (ADAGES). Fields were classified for severity using: (1) Advanced Glaucoma Intervention Study scoring system (AGIS), (2) Glaucoma Severity Staging system (GSS), and (3) Enhanced Glaucoma Severity Staging system (GSS-2). The following stages were compared: (s1) normal, (s2) mild/early/border, (s3) moderate, (s4) advanced/severe and (s5) end-stage. Mean defect (MD) and Visual Field Index (VFI) distributions across stages and classification systems were examined. Agreement in staging normal versus abnormal fields and severity staging across systems were assessed (Kappa statistic and matched-pair comparison).
Figure 1 shows the percentage of visual fields classified into each severity stage. Mean MD and VFI (±std) for fields staged as normal were: -0.4±1.3 and 99.4±0.7 for GSS; -0.6±1.2 and 98.9±1.3 for AGIS; -1.0±1.3 and 98.6±1.5 for GSS-2. Within GSS s4 and GSS-2 s3, two separate groups of MD and VFI scores were observed with peaks near -15/-5 and 56%/84% for GSS s4, and -7/-26 and 19%/80% for GSS2 s3. In staging normal versus abnormal fields, AGIS and GSS had moderate agreement (Κ=0.52±0.02); GSS and GSS-2 had fair agreement (Κ=0.36±0.02); AGIS and GSS-2 had moderate agreement (Κ=0.60±0.02). Visual fields tended to be staged with greatest severity using GSS and with least severity using AGIS (Wilcoxon sign-rank, p<0.05).
Monitoring glaucoma severity enables better follow-up and a more reliable prognosis. When selecting a classification system and comparing severity of visual fields across studies that use different staging systems, care should be taken to account for their differences.
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