Measuring the Contrast Sensitivity Function Using the qCSF Method With 10 Digits

Abstract

PurposeThe Bayesian adaptive quick contrast sensitivity function (qCSF) method with a 10-letter identification task provides an efficient CSF assessment. However, large populations are unfamiliar with letters and cannot benefit from this test. To overcome the barrier, we conducted this study.MethodA new font for digits (0∼9) was created. The digits were then filtered with a raised cosine filter, rescaled to different sizes to cover spatial frequencies from 0.5 to 16 cycles per degree (cpd), and used as stimuli in a 10-alternative forced choice (10AFC) digit identification task. With the 10AFC digit identification task, the CSFs of five young and five old observers were measured using the qCSF and Psi methods. The estimates from the latter served as reference.ResultsThe new digit font showed significantly improved similarity structure, Levene's test, F(1, 88) = 6.36, P = 0.014. With the 10-digit identification task, the CSFs obtained with the qCSF method matched well with those obtained with the Psi method (root mean square error [RMSE] = 0.053 log10 units). With approximately 30 trials, the precision of the qCSF method reached 0.1 log10 units. With approximately 75 trials, the precision of the CSFs obtained with the qCSF was comparable to that of the CSFs measured by the Psi method in 150 trials.ConclusionsThe qCSF with the 10 digit identification task is validated for both young and old observers.Translational RelevanceThe qCSF method with the 10-digit identification task provides an efficient and precise CSF test especially for people who are unfamiliar with letters.

Relationship of Contrast Sensitivity Measured Using Quick Contrast Sensitivity Function With Other Visual Functions in a Low Vision Population

“…The estimate of the variability of the qCSF measurements could be obtained by calculating the half-width of the 68.2% credible intervals (HWCI). 34 , 35 Finally, to compare the variability of the measured sensitivities of our low vision population with that of a control population, HWCI for single qCSF run of the study population were compared with the HWCI width of individuals with normal vision measured using the same device, but at a different viewing distance (4 m instead of 1 m) ( n = 17) (Lesmes LA, et al IOVS 2016;57(12):ARVO E-Abstract 5161). Calculating the width of the credible interval of the posterior distribution pt(τ) from a single qCSF run is an alternative method to estimate the variability of the measured sensitivity (the 68.2% HWCI for a Gaussian distribution is equal to the standard deviation of the distribution).…”

Mapping the Contrast Sensitivity of the Visual Field With Bayesian Adaptive qVFM

“…In characterizing spatial vision, the area under the log contrast sensitivity function is often used as a summary metric (Applegate et al, 1998 , 2000 ; Oshika et al, 1999 , 2006 ; van Gaalen et al, 2009 ; Hou et al, 2010 ; Lesmes et al, 2010 ; Jia et al, 2014 ; Dorr et al, 2015 ; Zheng et al, 2018 ). Here, we used the volume under the surface of the VFM (VUSVFM) to provide a summary metric of the entire visual field.…”

Comparing Spatial Contrast Sensitivity Functions Measured With Digit and Grating Stimuli

“…There is an added advantage that characters have distinct spatial structures and can be readily recognized without much effort. Indeed, a number of recent developments have shown that CSF tests with 10-alterantive forced choice tasks using either Sloan letters 24 or digits 25 are much more efficient than those with 2AFC grating tests. Because of the presence of multiple spatial channels in the visual system, 6 the contrast sensitivity function; that is, contrast sensitivity as a function of spatial frequency, measured with narrow-band stimuli provides a more comprehensive assessment of vision.…”

“…15,24,26 Many studies have used bandpass filtered letter or digit stimuli to assess the CSF. 24,25,27,28…”

“…35,36 The uneven similarities can make some alternatives more favored than others and, therefore, affect the test precision. Although the bandpass-filtered digit stimuli used in our previous study had a greatly improved similarity structure, 25 the effect of nonorthogonal stimuli on the estimated contrast sensitivities has not been systematically investigated to our knowledge.…”