Full-threshold versus Swedish Interactive Threshold Algorithm (SITA) in normal individuals undergoing automated perimetry for the first time

Abstract

Purpose: To compare the full-threshold (FT) and Swedish Interactive Threshold Algorithm standard (SS) strategies in normal individuals undergoing automated perimetry for the first time.

Design: Randomized, comparative, observational case series.

Participants: Eighty perimetrically naive normal individuals.

Methods: All individuals underwent computerized visual field examinations (30-2, Humphrey 750, Humphrey-Zeiss, Dublin, CA) with both FT and SS strategies. One eye of each individual was tested. Test order between strategies was randomized.

Main outcome measures: The following variables were compared: test time, foveal threshold, fixation losses, false-positive and false-negative errors, mean deviation, pattern standard deviation, glaucoma hemifield test, and number of depressed points deviating at P < 5%, P < 2%, P < 1%, and P < 0.5% on the total and pattern deviation probability maps. Initially, we compared the results of all FT and SS tests, regardless of the order in which they were applied. Next, patients undergoing SS as the first examination were compared with those undergoing FT as the first test. Finally, the SS and FT results obtained in the second test were compared. Anderson's criteria were applied to define abnormal examinations, allowing for the calculation of the specificity of the SS and FT strategies.

Results: When the results of all FT and SS tests were analyzed, the number of significantly depressed points deviating at P < 5%, P < 2%, and P < 1% on the pattern deviation probability maps was higher with the SS strategy (P < 0.05); the specificity was 50% for SS and 72.5% for FT (P < 0.01). When only first examinations were compared, the number of significantly depressed points deviating at P < 5%, P < 2%, and P < 1% on both the total and pattern deviation probability maps was higher with the SS strategy (P < 0.05); the specificity was 38.1% and 63.2% for the SS and FT strategies, respectively (P = 0.04). When only the second examinations were compared, there were no significant differences either between the number of depressed points or between the specificities of both strategies (73.7% for SS and 71.4% for FT) (P = 0.98).

Conclusions: Normal individuals with no perimetric experience may present more significantly depressed points on the pattern deviation probability map when the SS strategy is used, reducing the test specificity in comparison with FT. These findings are probably due to a lower interindividual variability observed with SS. However, these differences disappeared in a second examination, suggesting that both strategies perform similarly in perimetrically experienced individuals.