Comparison of the Humphrey swedish interactive thresholding algorithm (SITA) and full threshold strategies

To compare the Swedish interactive thresholding algorithm (SITA) strategy with the full threshold strategy in routine clinical practice.

Using the Humphrey visual field analyzer model 750 (Allergan Humphrey, San Leandro, CA), 108 subjects were tested with 24-2 SITA (version A9) and 24-2 full threshold strategies. Test results were compared for time taken and reliability and on the basis of seven criteria of abnormality.

The SITA required on average 48.8% less time than the full threshold strategy. Patient reliability parameters were somewhat better with SITA. There was a strong correlation between mean deviation and pattern standard deviation. Average threshold sensitivity at each point was increased by 1.31 dB with SITA, but greater differences were seen at points with lower sensitivity. Using the full threshold strategy as our standard for comparison, the sensitivity of SITA varied from 83.0% to 93.2% in detecting the variously defined abnormalities. Fields shown as normal with full threshold strategy corresponded with those found to be normal with SITA in 79.0 to 96.3% cases depending on criteria for abnormality. There were a few cases in which SITA suggested an early abnormality but results of full threshold testing remained normal. On average, the size and depth of scotomas decreased slightly with SITA, but this difference was not statistically significant. Of the 70 patients surveyed about their preference, 65 (92.9%) preferred SITA.

Full threshold and SITA strategies are comparable in detecting glaucomatous defects. The SITA strategy requires significantly less time to perform and is a satisfactory alternative to full threshold algorithms in clinical practice for diagnosis and management of glaucoma.