Influence of the rate of contrast change on the quality of contrast sensitivity assessment: a comparison of three psychophysical methods.
Criterion-free forced-choice procedures for measuring contrast sensitivity with a cathode ray tube (CRT) have low within-subject, intersubject, and test-retest variabilities, but a long test time compared with psychophysical methods that rely on the subject's criterion to determine threshold. Test time and variability of criterion-dependent methods depend on the rate at which the contrast changes on the CRT display. This study compared two criterion-dependent psychophysical methods for measuring contrast sensitivity (the method of increasing contrast and the von Békésy tracking method) with a criterion-free two-alternative forced-choice procedure. A range of rates of contrast change was studied: 0.1, 0.3, 0.5, 0.7 and 1.0 log unit s-1. Contrast sensitivity, within-subject variability, intersubject variability, test-retest variability, and test time of the three methods were compared. The 2-AFC procedure performed best with regard to within-subject, intersubject, and test-retest variabilities. A time-efficient alternative was the von Békésy tracking method at rates between 0.1 and 0.5 log unit s-1.
Nio
Y K
YK
Laboratory of Experimental Ophthalmology, University of Groningen, PO Box 30.001, 9700 RB Groningen, The Netherlands. k.nio@gelre.nl
Jansonius
N M
NM
Lamers
P
P
Mager
A
A
Zeinstra
J
J
Kooijman
A C
AC
D000328:Adult; D015350:Contrast Sensitivity; D006801:Humans; D011601:Psychophysics; D015203:Reproducibility of Results; D012684:Sensory Thresholds; D014787:Vision Tests / Q000295:instrumentation / Q000379:methods*