Method and apparatus for measuring contrast sensitivity

A method of measuring the contrast sensitivity of a subject, comprising the steps of:

• displaying chains of grating stimuli at randomly interleaved spatial frequencies, each of said grating stimuli consisting of first and second color bars and having one of two alternative orientations;
• prompting the subject to identify the orientation of each of said grating stimuli from said one of two alternative orientations;
• and
• varying the contrast level of the next grating stimulus according to whether the subject correctly identified the orientation of the previous grating stimulus, wherein a correct response decreases the contrast level of the next grating stimulus in the chain by a first amount, S_down, and whereas an incorrect response increases the contrast level by a second amount, S_up.

A method of measuring the contrast sensitivity of a subject, comprising the steps of:

• displaying chains of grating stimuli at randomly interleaved spatial frequencies, each of said grating stimuli consisting of first and second color bars and having one of two alternative orientations;
• prompting the subject to identify the orientation of each of said grating stimuli from said one of two alternative orientations;
• and
• varying the pseudo-color contrast level of the next grating stimulus according to whether the subject correctly identified the orientation of the previous grating stimulus, wherein a correct response decreases the pseudo-contrast level of the next grating stimulus in the chain by a first amount, S_down, and whereas an incorrect response increases the pseudo-contrast level by a second amount, S_up.