Evaluation of a new threshold visual field strategy, SITA, in normal subjects. Swedish Interactive Thresholding Algorithm.

Abstract

We developed a new family of test algorithms. This is an evaluation in normal subjects. One eye in each of twenty normal subjects, with a mean age of 37 years (range 26 to 59), was tested twice with each of the SITA, Full Threshold and Fastpac strategies of the Humphrey perimeter at 3 separate visits. Actual test times and number of stimulus exposures were compared. Test-retest variability and levels of threshold estimates were also calculated and compared between strategies. In all subjects test times were shortest with SITA, 6.14 minutes in average, which was 50% as compared to Full Threshold (p<0.001) with an average of 12.27 minutes, and a reduction of 16% as compared to Fastpac (mean 7.28 minutes, p<0.0001). SITA required 287 stimulus exposures on the average, significantly fewer (p<0.0001) than corresponding numbers with Full Threshold (mean of 404), and significantly more (p<0.0001) than with Fastpac (average 240). SITA results showed significantly lower test-retest variability than results obtained with Fastpac (p=0.0002), and just as low as those of the Full Threshold strategy (p=0.0979). Threshold values obtained with SITA were slightly higher than those produced by the other two strategies. The results confirm those of previously reported simulated tests, that improved test algorithms using advanced visual field models and mathematical analyses performed in real time may effectively shorten computerized perimetry tests, while achieving the same or better test quality than today's standard methods.