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Luis Lesmes, Jennifer Wallis, Mary Lou Jackson, Peter Bex; The Reliability of the quick CSF Method for Contrast Sensitivity Assessment in Low Vision. Invest. Ophthalmol. Vis. Sci. 2013;54(15):2762. doi: https://doi.org/.
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© ARVO (1962-2015); The Authors (2016-present)
The contrast sensitivity function (CSF) presents a better characteristic of functional vision than visual acuity. The quick CSF is a novel adaptive method that greatly reduces CSF testing times, using Bayesian adaptive inference and a trial-to-trial information gain strategy. In an application of the quick CSF to assess low vision (Lesmes et al, ARVO 2012), we reported that only 2-3 minutes (15 trials) were needed to obtain estimates of the area under the log CSF (AULCSF), which were correlated with Pelli-Robson contrast sensitivity. The current study was designed to complement the previous demonstration of method accuracy, and assess method reliability using repeated measurements in patients with normal and impaired vision.
CSF assessments were obtained from people with normal and impaired vision. Each observer completed two CSF tests (~3 minutes each). Reliability was assessed via the AULCSF difference scores, calculated between estimates obtained from repeated CSF assessments.
Two important results were: (1) AULCSF estimates obtained in normal vision were slightly more reliable than those in impaired vision and (2) in both groups, AULCSF estimates demonstrated greater reliability with increasing test length. For normal vision, differences between repeated AULCSF estimates exhibited a coefficient of variation (CV) of ~15% after 15 trials and <10% after 20 trials. For impaired vision, CV values were ~20% after 15 trials and <15% after 20 trials. This level of variability, considered between repeated measurements, is small when compared to the individual differences (population variability) in sensitivity exhibited in either the normal or impaired vision groups.
These results suggest that the quick CSF provides a rapid and reliable contrast sensitivity assessment in normal and impaired vision. The broad contrast sensitivity measure provided by the AULCSF, which can be assessed in a short, clinically practical testing time, demonstrates potential value as a functional endpoint for clinical practice and clinical trials.
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