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Abstract #8429 Published in IGR 5-1
Misleading statistical calculations in far-advanced glaucomatous visual field loss
Blumenthal EZ; Sapir-Pichhadze ROphthalmology 2003; 110: 196-200
OBJECTIVE: In this study, the capability of statistical analysis indices to characterize static automated visual fields (VFs) accurately in cases of far-advanced glaucoma was assessed. DESIGN: Retrospective observational case series. PARTICIPANTS: Sixteen eyes of 15 patients with end-stage glaucoma and evidence of collapse of VF statistical analysis indices were included in the study. METHODS: End-stage glaucoma was defined as vertical cup-to-disc ratio of 0.9 or more, mean deviation less than -24 dB and with only a central or temporal island remaining in the VF gray scale. Collapse of statistical indices was defined as any of the following: pattern deviation probability plot without a single VF location showing p < 0.5%; corrected pattern standard deviation (CPSD) and pattern standard deviation (PSD) probability less than 5% or within normal limits (WNL); short-term fluctuation (SF) probability WNL; glaucoma hemifield test (GHT) not outside normal limits (ONL); or presence of a low patient reliability comment triggered by 40% or more false-negative (FN) responses. MAIN OUTCOME MEASURES: Visual field statistical indices. RESULTS: Of the 16 VFs showing misleading statistical calculations, nine of 16 eyes had a normal pattern deviation probability plot. The PSD, SF, and CPSD parameters were normal or barely outside the normal range in four of 16, ten of 16, and five of 16 eyes, respectively. The GHT was ONL in seven of 13 eyes, borderline with generalized reduction of sensitivity (GRS) in three eyes, and only GRS in two additional eyes. Low patient reliability was triggered because of an FN score of 40% or more in ten of 16 eyes. CONCLUSIONS: Statistical indices are crucial for the interpretation of automated static VFs. However, in end-stage glaucomatous VF loss, both summary statistical indices and reliability indices may not detect abnormality, thus misleading the casual observer.
Dr. E.Z. Blumenthal, Department of Ophthalmology, Hadassah University Hospital, and Hebrew University-Hadassah Medical School, Jerusalem, Israel. eblumenthal@md.huji.ac.il
Classification:
6.6.2 Automated (Part of: 6 Clinical examination methods > 6.6 Visual field examination and other visual function tests)