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Lenka Musilova, Frantisek Pluhacek, Harold E. Bedell, Stephanie Marten-Ellis, John Siderov; Peripheral contour interaction is similar under photopic and scotopic luminances. Invest. Ophthalmol. Vis. Sci. 2017;58(8):4217.
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© ARVO (1962-2015); The Authors (2016-present)
The characteristics of peripheral contour interaction are well documented for photopic conditions. The aim of this study is to compare peripheral contour interaction (CI) under photopic and scotopic luminances.
We analysed the data of 9 normal observers in two laboratories (Palacky University Olomouc, Czech Republic (PU) and University of Houston, USA (UH)), who viewed randomly selected individual Sloan letters surrounded by 4 equally spaced bars for several edge-to-edge separations. Stimuli were viewed peripherally at eccentricities of 6 and 12 deg (PU) and 5 and 10 deg (UH) under photopic and scotopic conditions. Percent correct letter identification for each subject was fitted by a cumulative normal density curve that ranged from a guessing level of 10% to an estimated upper asymptote (100% – λ). The extent and magnitude of CI were defined from these fitted functions and statistically analysed using repeated-measures ANOVAs.
The estimated mean angular extent of CI ranged from 25 to 102 min arc for photopic luminance levels and from 29 to 77 min arc under scotopic levels for all eccentricities. The magnitude of CI ranged from 47% to 69% photopically and from 56% to 81% scotopically. The extent and magnitude of the PU data showed no significant effect of luminance, eccentricity or their interaction. The magnitudes of CI measured at UH also were unaffected by luminance or eccentricity, but the extent of CI increased significantly with increasing eccentricity. As for the PU data, the effects of luminance and eccentricity x luminance interaction were insignificant.
Peripheral CI does not show consistent differences between photopic and scotopic luminance levels. The only previous study of scotopic CI (Simunovic & Calver, 2004) found a markedly smaller extent than had been reported for the interaction between photopic stimuli, a conclusion that can be attributed to an inappropriate comparison between scotopic CI and photopic crowding functions.
This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.
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