False Positive Responses in Standard Automated Perimetry

Purpose: To analyze the relationship between rates of false positive (FP) responses and standard automated perimetry results. Design: Prospective multicenter cross-sectional study. Methods: One hundred twenty-six patients with manifest or suspect glaucoma were tested with Swedish Interactive Thresholding Algorithm (SITA) Standard, SITA Fast, and SITA Faster at each of 2 visits. We calculated intervisit differences in mean deviation (MD), visual field index (VFI), and number of statistically significant test points as a function of FP rates and also as a function of general height (GH). Results: Increasing FP values were associated with higher MD values for all 3 algorithms, but the effects were small, 0.3 dB to 0.6 dB, for an increase of 10 percentage points of FP rate, and for VFI even smaller (0.6%-1.4%). Only small parts of intervisit differences were explained by FP (r² values 0.00-0.11). The effects of FP were larger in severe glaucoma, with MD increases of 1.1 dB to 2.0 dB per 10 percentage points of FP, and r² values ranging from 0.04 to 0.33. The numbers of significantly depressed total deviation points were affected only slightly, and pattern deviation probability maps were generally unaffected. GH was much more strongly related to perimetric outcomes than FP. Conclusions: Across 3 different standard automated perimetry thresholding algorithms, FP rates showed only weak associations with visual field test results, except in severe glaucoma. Current recommendations regarding acceptable FP ranges may require revision. GH or other analyses may be better suited than FP rates for identifying unreliable results in patients who frequently press the response button without having perceived stimuli.