Foveal contour interaction for low contrast acuity targets

John Siderov, Sarah J. Waugh, Harold E. Bedell

Research output: Contribution to journalArticlepeer-review

34 Citations (Scopus)


Previous investigators reported the impairment of foveal visual acuity by nearby flanking targets (contour interaction) is reduced or eliminated when acuity is measured using low contrast targets. Unlike earlier studies, we compared contour interaction for high and low contrast acuity targets using flankers at fixed angular separations, rather than at specific multiples of the acuity target's stroke width. Percent correct letter identification was determined in 4 adult observers for computer generated, high and low contrast dark Sloan letters surrounded by 4 equal contrast flanking bars. Two low contrast targets were selected to reduce each observer's visual acuity by 0.2 and 0.4 log. MAR. The contour interaction functions measured for high and low contrast letters are very similar when percent correct letter identification is plotted against the flanker separation in min arc. These results indicate that contour interaction of foveal acuity targets occurs within a fixed angular zone of a few min arc, regardless of the size or contrast of the acuity target.

Original languageEnglish
Pages (from-to)10-13
Number of pages4
JournalVision Research
Early online date28 Nov 2012
Publication statusPublished - 25 Jan 2013
Externally publishedYes


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