PURPOSE: To evaluate the specificity of the Threshold Noiseless Trend program (TNT), designed to measure progression in visual fields, using four procedures. MATERIALS AND METHODS: A. In 63 eyes with ocular hypertension, whose last examination showed no perimetric or morphological defects, we performed a mean of 7.70 +/- 1.71 follow-up examinations during 2.2 +/- 0.6 years. B. In 81 glaucomatous eyes examined twice with a bracketing strategy (Octopus 1-2-3 perimeter), we calculated mean threshold value and long-term fluctuation. We simulated 12 different visual fields, adding a random component to simulate an equivalent fluctuation of amplitude. C. Seventy-two glaucomatous eyes, with and without progression, were examined 7.76 +/- 1.25 times during 4.88 +/- 1.39 years using the Humphrey-Sita Standard strategy. Visual field tests were randomly disordered and analyzed using TNT. D. 1221 eyes were examined 7.19 +/- 3.5 times during 3.50 +/- 1.45 years (10,407 visual fields) using TOP-G1 program. We detected progression in 204 eyes using TNT. They were re-evaluated after random disordering of visual field tests. RESULTS: The four procedures indicated specificity > or = 95% as from the seventh examination; this reduced to 90% in experiment C with six examinations, and in experiments A and C with five examinations. CONCLUSIONS: The specificity of TNT may be considered to be over 95% with a large number of examinations, and 90-100% with fewer examinations. At least five examinations are required for a basic interpretation of progression, and preferably more than six to guarantee the specificity of the result.
PURPOSE: To evaluate the specificity of the Threshold Noiseless Trend program (TNT), designed to measure progression in visual fields, using four procedures. MATERIALS AND METHODS: A. In 63 eyes with ocular hypertension, whose last examination showed no perimetric or morphological defects, we performed a mean of 7.70 +/- 1.71 follow-up examinations during 2.2 +/- 0.6 years. B. In 81 glaucomatous eyes examined twice with a bracketing strategy (Octopus 1-2-3 perimeter), we calculated mean threshold value and long-term fluctuation. We simulated 12 different visual fields, adding a random component to simulate an equivalent fluctuation of amplitude. C. Seventy-two glaucomatous eyes, with and without progression, were examined 7.76 +/- 1.25 times during 4.88 +/- 1.39 years using the Humphrey-Sita Standard strategy. Visual field tests were randomly disordered and analyzed using TNT. D. 1221 eyes were examined 7.19 +/- 3.5 times during 3.50 +/- 1.45 years (10,407 visual fields) using TOP-G1 program. We detected progression in 204 eyes using TNT. They were re-evaluated after random disordering of visual field tests. RESULTS: The four procedures indicated specificity > or = 95% as from the seventh examination; this reduced to 90% in experiment C with six examinations, and in experiments A and C with five examinations. CONCLUSIONS: The specificity of TNT may be considered to be over 95% with a large number of examinations, and 90-100% with fewer examinations. At least five examinations are required for a basic interpretation of progression, and preferably more than six to guarantee the specificity of the result.