Comparing the shape of contrast sensitivity functions for normal and low vision

Susana T.L. Chung, Gordon E. Legge

Research output: Contribution to journalArticlepeer-review

30 Scopus citations

Abstract

PURPOSE. The contrast sensitivity function (CSF) provides a detailed description of an individual’s spatial-pattern detection capability. We tested the hypothesis that the CSFs of people with low vision differ from a “normal” CSF only in their horizontal and vertical positions along the spatial frequency (SF) and contrast sensitivity (CS) axes. METHODS. Contrast sensitivity for detecting horizontal sinewave gratings was measured with a two temporal-interval forced-choice staircase procedure, for a range of SFs spanning 5 to 6 octaves, for 20 low-vision observers and five adults with normal vision. An asymmetric parabolic function was used to fit the aggregate data of the normal-vision observers, yielding the “normal template.” Each of the 20 low-vision CSFs was fit in two ways, by using a shapeinvariant version of the normal template (with the width parameters fixed) that was shifted along the log-SF and log-CS axes, and by an unconstrained asymmetric parabolic function (“free-fit”). RESULTS. The two fitting methods yielded values of the peak CS, the SF corresponding to peak CS, and the high cut-off SF that were highly correlated and in good agreement with each other. In addition, the width parameters of the low-vision CSFs were comparable with those of the normal template, implying that low-vision CSFs are similar in shape to the normal CSF. CONCLUSIONS. The excellent agreement of parameters estimated by the two fitting methods suggests that low-vision CSFs can be approximated by a normal CSF shifted along the log-SF and log-CS axes to account for the impaired acuity and contrast sensitivity.

Original languageEnglish (US)
Pages (from-to)198-207
Number of pages10
JournalInvestigative Ophthalmology and Visual Science
Volume57
Issue number1
DOIs
StatePublished - Jan 2016

Bibliographical note

Funding Information:
Supported by research Grants R01-EY012810 (STLC) and R01-EY017835 (GEL) from the National Institutes of Health (Bethesda,MD, USA).

Publisher Copyright:
© 2016, Association for Research in Vision and Ophthalmology Inc. All rights reserved.

Keywords

  • Contrast sensitivity function
  • Low vision
  • Psychophysics
  • Spatial vision

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