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S. E. Bandermann, J. L. Keltner, C. A. Johnson, K. E. Cello, M. A. Kass, M. O. Gordon, Ocular Hypertension Treatment Study Group; A Comparison of Full Threshold and Swedish Interactive Threshold Algorithms (SITA) Testing Procedures in the Ocular Hypertension Treatment Study (OHTS). Invest. Ophthalmol. Vis. Sci. 2007;48(13):1643.
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To compare the Glaucoma Hemifield Test (GHT) analysis using the Full Threshold and Swedish Interactive Threshold Algorithms (SITA) testing procedures in the Ocular Hypertension Treatment Study (OHTS).
Because the GHT index is one criterion in the definition of POAG in the OHTS, we sought to determine whether there were any differences between Full Threshold and SITA testing procedures. The GHT compares asymmetry of the superior and inferior hemifields and classifies these asymmetries into five groups: (1) Within normal limits, (2) Borderline, (3) Outside Normal Limits, (4) General Reduction in Sensitivity, and (5) Abnormally High Sensitivity. We compared the distribution of these classifications when the OHTS protocol used the Full Threshold testing procedures and when it changed to the SITA testing procedures beginning August 1, 2003.
No differences were detected between the GHT index of the Full Threshold and SITA Standard strategies for the categories of within normal limits, borderline, outside normal limits and general reduction in sensitivity. However, as of November 1, 2006, 0.1% (53/46,504) of the Full Threshold visual fields and 1.06% (158/14,690) of the SITA strategy visual fields had a GHT outcome of abnormally high sensitivity. The correlation among the visual fields from the same patient was adjusted using the Generalized Estimating Equation (GEE) technique. It was found that the SITA Standard 30-2 fields were 9.53 times more likely than Full Threshold fields to have an abnormally high sensitivity outcome in the GHT index (p < 0.0001).
There was nearly a ten-fold increase in the number of abnormally high sensitivity determinations for SITA Standard in comparison to Full Threshold. The basis for this effect is not clear but has remained persistent throughout follow-up visual field testing in the OHTS over the past three years.
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