Abstract

In the study of visual disorders, contrast sensitivity has been measured with both windowed sinusoidal gratings and with letters. It has been suggested that contrast sensitivity functions for both types of stimuli are quite similar (e.g., Legge et al., 1987; Herse and Bedell, 1989), although comparisons have not been made under comparable conditions. While sinusoidal stimuli are advantageous for studying spatial mechanisms, letters are more familiar to patients, contain multiple orientations, are less subject to spurious resolution and are more affected by sampling irregularity than are gratings (Herse and Bedell, 1989), all of which suggest that the measurement of contrast sensitivity for letters may have an advantage in detecting visual abnormalities. However, letters contain a broad range of spatial frequencies (Parish and Sperling, 1991) which potentially complicates the interpretation of test results using these stimuli.

© 1992 Optical Society of America