Purchase this article with an account.
Sarah J Waugh, Monika A Formankiewicz, M Izzuddin Hairol; Contour interaction extents (in MAR) for differently-sized Cs vary little within, but lots between, LM and CM acuity systems.. Journal of Vision 2012;12(9):101. doi: 10.1167/12.9.101.
Download citation file:
© ARVO (1962-2015); The Authors (2016-present)
Visual acuity for contrast-modulated (CM) Cs is ~0.3logMAR higher than for luminance-modulated (LM) Cs, consistent with larger summation areas for CM stimuli (Hairol et al, VSS2010; Sukumar & Waugh, 2007). The extent of contour interaction for LM and CM Cs is similar when scaled for letter size, which implies a fixed extent for each letter processing system. However, acuity studies themselves employ a range of letter sizes. In this study we assessed whether fixed letter sizes and spatial extents scale in MAR, within and between, LM and CM spatial acuity systems. First, we revisited contour interaction on visual acuity data (Formankiewicz et al, VSS2010). Psychometric functions generated were compared for same size Cs, and extents estimated across ~2.5x range of sizes for LM and CM systems. Performance functions for contour interaction were also measured using fixed sized Cs on new observers. The 80% performance level was selected for unflanked Cs and then bars were placed 1-200 arcmin from the C. C modulation depth was varied and data for a 5-6.5x range of C sizes for both the LM and CM systems (LM: logMAR 0.1 to 0.9 and CM: logMAR 0.6 to 1.3) was gathered. Foveal visual acuity data revealed that within a system, larger letters do not consistently produce larger contour interaction extents (in MAR). When different letter sizes are required by the LM and CM systems, spatial extents are different. Performance function data confirm that extents vary little within each system (LM 1-3 arcmin; CM 6-12 arcmin). Foveal C acuity displays contour interaction extents that do not systematically vary, despite differences in letter size. Across LM and CM systems, acuities and extents are different. The results have implications for visual acuity processing of LM and CM stimuli and on masking models of foveal contour interaction.
Meeting abstract presented at VSS 2012
This PDF is available to Subscribers Only