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Measurement of contrast sensitivity curve is based on 4 gratings at 2 contrast levels,
10%, and 2.5% contrast using 2 grating frequencies: 0.5 cpcm and 8 cpcm (10% level)
or 0.5 cpcm and 4 cpcm (2.5% level). Testing is based on finding the distance where the
person is at threshold in seeing the direction of the grating lines. Includes nomograms,
instructions, and recording forms. Measures 8″ (20 cm) in diameter. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 253400