These discs measure contrast sensitivity curve based on 4 gratings at 2 contrast levels: 10% and 2.5% contrast. These 2 levels use 2 grating frequencies: the 10% level uses 0.5 cpcm and 8 cpcm while the 2.5% level uses 0.5 cpcm and 4 cpcm. Testing is based on finding the distance where the person is at the threshold in seeing the direction of the grating lines. Includes nomograms, instructions, recording forms, and 2 double-sided discs.

Dimensions: 8" (20 cm) in diameter.