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Rajkumar Nallour Raveendran, Arun kumar Krishnan, Ben Thompson; Reduced fixation stability during a peripheral orientation discrimination task in participants with normal vision. Invest. Ophthalmol. Vis. Sci. 2018;59(9):1274. doi: https://doi.org/.
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© ARVO (1962-2015); The Authors (2016-present)
The main purpose of the study was to assess the effect of peripheral task performance on fixation stability.
Within a prospective, observational study, nine observers [(age: 37±6 yrs), VA; 20/20 or better] performed a tumbling E orientation discrimination task at three eccentricities (0°, 5° and 10°). The task was performed with and without flankers (vertically and horizontally positioned E optotypes). A central fixation cross was provided for the two peripheral viewing conditions and optotype size was scaled for each eccentricity. Monocular fixational eye movements of the dominant eye were measured using an EyeLink 1000+ IR video based eyetracker. Fifteen trials were presented within a block and there were 4 blocks for each eccentricity. Fixation stability was calculated as 1SD or 68% bivariate contour ellipse area (BCEA). BCEA values were log10 transformed for repeated measured ANOVA analysis and post-hoc tests (Tukey HSD).
BCEA was significantly larger (less stable fixation) when targets were presented at eccentric locations compared to the 0° position (main effect of eccentricity [F(2,16)=22.14;p<0.001]; pairwise comparisons, p<0.001 for both the 5° and 10° eccentricities). This effect was not influenced by the presence or absence of flankers, suggesting that it was not related to crowding [F(2, 16)=1.3901, p=0.28]. The presence of flankers significantly increased BCEA for the 0° position relative to the no-flankers condition (p = 0.01), but not at the 5° (p=0.66) or 10° (p=0.06) positions.
Fixation stability decreased when the orientation discrimination task was presented in peripheral vision. This effect was not influenced by crowding and may be due to a covert attentional shift away from central vision.
This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.
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