Abstract
The contrast sensitivity function (CSF) relates the visibility of a spatial pattern to both its size and contrast, and is therefore a more comprehensive assessment of visual function than acuity, which only determines the smallest resolvable pattern size. Because of the additional dimension of contrast, estimating the CSF can be more time-consuming. Here, we compare two methods for rapid assessment of the CSF that were implemented on a tablet device. For a single-trial assessment, we asked 63 myopes and 38 emmetropes to tap the peak of a “sweep grating” on the tablet’s touch screen. For a more precise assessment, subjects performed 50 trials of the quick CSF method in a 10-AFC letter recognition task. Tests were performed with and without optical correction, and in monocular and binocular conditions; one condition was measured twice to assess repeatability. Results show that both methods are highly correlated; using both common and novel measures for test-retest repeatability, however, the quick CSF delivers more precision with testing times of under three minutes. Further analyses show how a population prior can improve convergence rate of the quick CSF, and how the multi-dimensional output of the quick CSF can provide greater precision than scalar outcome measures.
Highlights
The contrast sensitivity function (CSF) relates the visibility of a spatial pattern to both its size and contrast, and is a more comprehensive assessment of visual function than acuity, which only determines the smallest resolvable pattern size
We evaluate the quick CSF method in a population of healthy observers, and we further investigate the effect on choosing different priors on its robustness
Solid lines indicate univariate linear regression and shaded regions indicate 95% confidence intervals. Both dimensions of the single-trial assessment are correlated with AULCSF (p ≪ 0.01, R2 = 0.34 for peak sensitivity and R2 = 0.40 for peak frequency); multivariate regression explains more of the variance (p ≪ 0.01, R2 = 0.54) with no statistically significant interaction between peak sensitivity and peak frequency (p = 0.59)
Summary
The contrast sensitivity function (CSF) relates the visibility of a spatial pattern to both its size and contrast, and is a more comprehensive assessment of visual function than acuity, which only determines the smallest resolvable pattern size. Tests were performed with and without optical correction, and in monocular and binocular conditions; one condition was measured twice to assess repeatability Results show that both methods are highly correlated; using both common and novel measures for test-retest repeatability, the quick CSF delivers more precision with testing times of under three minutes. The CSF is typically assessed by estimating individual thresholds for a range of spatial frequencies, using one-dimensional Bayesian adaptive methods[14] This precise approach is too time-consuming for regular clinical care, and the currently prevalent paper charts require substantial trade-offs such as coarse stimulus space resolution that might restrict variation to either spatial frequency or contrast, and simple scoring rules that can be applied manually; this has sometimes led to the introduction of idiosyncratic scoring rules, making it hard to compare results across laboratories or even individual examiners[15,16]. Even for computerized testing, the upper limits of visual contrast sensitivity in healthy subjects
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