Abstract
Purpose:
The contrast sensitivity function (CSF) provides a comprehensive characterization of spatial vision and predicts functional vision better than acuity, but long testing times prevent its psychophysical assessment in clinical applications. Lesmes et al (2010) developed the qCSF method to obtain precise CSF measurements in only 50 trials with a 2AFC grating orientation identification task. Simulation studies suggest that a 10AFC task, with a 10% guessing level, would further improve the test efficiency. We tested this prediction using a 10AFC letter identification task. In addition, we compared CSFs obtained from the 2AFC and 10AFC procedures over a wide range of testing conditions; evaluated the relationship between CSF cutoff frequency with visual acuity; applied the multi-channel contrast-gain control model (MCM, Huang et al, 2011) to model binocular summation in binocular CSFs.
Methods:
A 10-letter filtered Sloan letter set and ± 45° sinewave gratings served as stimuli. Visual acuities and CSFs of 4 myopic participants were measured in 4 monocular (left eye uncorrected, left eye corrected, right eye uncorrected, right eye corrected) and 4 binocular (left eye corrected only, right eye corrected only, both eyes uncorrected, and both eyes corrected) conditions at a 5 m viewing distance. The 10AFC and 2AFC procedures were directly compared.
Results:
We found that (1) the precision of CSFs obtained in 15 trials of the 10AFC procedure matched that from 50 trials of the 2AFC procedure, (2) the CSFs obtained from the two procedures are highly correlated (r = 0.95 ± 0.03), (3) The cutoff frequencies obtained from both procedures are highly correlated with visual acuity (r = 0.91 and 0.91, respectively) with no significant difference (p = 0.46), (4) the MCM provided an excellent account of the data in all the viewing conditions (r2 > 95%), and allowed us to quantify the relative efficiency of the two eyes in a wide range of spatial frequencies.
Conclusions:
The 10AFC qCSF procedure is much more efficient than the 2AFC procedure. CSFs obtained from the two procedures are highly correlated. Cutoff frequencies of the CSFs obtained from qCSF are highly correlated with visual acuity. Monocular and binocular CSFs can be modeled with the MCM to quantify the relative efficiency of the two eyes in a wide range of spatial frequencies.
Keywords: 478 contrast sensitivity