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T. Kohnen, J. Buehren, E. Terzi, M. Bach, W. Wesemann; The Frankfurt-Freiburg Contrast and Acuity Test System (FF-CATS): A New Test to Determine Contrast Sensitivity at Different Luminance Levels . Invest. Ophthalmol. Vis. Sci. 2003;44(13):2592.
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Purpose: To evaluate a newly designed computer-based test system for the measurement of contrast thresholds at different luminance levels. Methods: The FF-CATS is a psychophysical test based on the Freiburg Visual Acuity Test (FVAT) using an 8-alternative forced choice procedure and the best PEST (parameter estimation by sequential testing) algorithm to measure automatically and observer-independently acuity and contrast thresholds. Landolt rings of 100’ in diameter (Snellen equivalent 20/400) are displayed at different contrasts on a high resolution monitor at 167 cd/m². For testing at the scotopic luminance level (0.167 cd/m²), a neutral filter withτ=10-3 was used to reduce monitor luminance. 40 eyes of 40 volunteers (group I: 20 eyes, age 21-47 years; group II: 20 eyes, age 54-69 years) were examined with the FF-CATS and with the Functional Acuity Contrast Test (F.A.C.T.) at 0.167 cd/m² and 167 cd/m² and with the Pelli-Robson chart (PRC) at 100 cd/m². Tests were performed with and without glare in a randomized order. The whole test sequence was repeated at least one hour later. The tests were assessed concerning discrimination between group I and II (receiver operation characteristic), repetability (Bland-Altmann comparison) and validity (correlation with higher order wavefront aberrations measured with a Hartmann-Shack sensor). Results: The FF-CATS discriminated better between the two groups (Az ROC=0.93) than FACT (0.67) or PRC (0.85). Coefficients of repetability [logCS] were 0.38 for the FF-CATS, 0.25 for the FACT and 0.21 for the PRC. Results were similar for measurements at 0.167 cd/m² and for measurements with glare. The FF-CATS showed highest correlation with HOA RMS (r=-0.55, p<0.001), compared to FACT (r=-0.14, p=0.46) and PRC (r=-0.45, p<0.01). Conclusions: The FF-CATS is a reliable, sensitive and valid test to determine contrast sensitivity at different luminance levels with and without glare.
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