A Comparison of False-negative Responses for Full Threshold and SITA Standard Perimetry in Glaucoma Patients and Normal Observers

Abstract

To compare false-negative (FN) rates for Full Threshold (FULL) and Swedish Interactive Threshold Algorithm (SITA) Standard automated perimetry in healthy control subjects and glaucoma patients. One eye of 19 glaucoma patients and 5 normal control subjects underwent 5 visual field examinations within 6 weeks on the Humphrey Field Analyzer II using the 24-2 FULL and SITA testing procedures. The order of presentation of test procedures was counterbalanced across participants. We obtained FN response procedures that presented stimuli 9 dB greater than a previously determined threshold value at specific locations in the visual field (FULL) or up to 20 dB greater than the threshold value (SITA), and evaluated whether the patient responded to these suprathreshold stimuli. We compared the percentage of FN responses for the FULL and SITA tests before (Peridata output) and after postprocessing of data. The percentage of FNs was almost twice as high for FULL testing compared with the 2 SITA analyses. The SD of FN percentages was half as large for SITA postprocessing compared with FULL and SITA Peridata procedures. Because the distributions were not normally distributed, a Kruskal-Wallis analysis of variance was performed and revealed a statistically significant difference (H=13.094, P<0.001) for FN percentages among the 3 evaluations. FULL test procedures yield about twice as many FNs as SITA procedures. This may be related to the SITA method of testing for FN in relatively normal areas as opposed to any location (even if it has low sensitivity) with FULL. Because FN responses can be due to either high variability in damaged areas or pathologic variations, these revised FN procedures provide greater assistance in properly interpreting visual field results.