Purchase this article with an account.
Linh Dang, Laura Walker Renninger, Donald Fletcher; Stability of eccentric attention. Journal of Vision 2009;9(8):393. doi: https://doi.org/10.1167/9.8.393.
Download citation file:
© ARVO (1962-2015); The Authors (2016-present)
Purpose: Patients with macular degeneration develop eccentric fixation by directing objects of interest and attention to preferred retinal locus (PRL). This study explores the relationship between PRL eccentricity and fixation stability. We hypothesized that fixation stability would decrease as the deviation between gaze and attention increased.
Method: An experienced low vision observer with two PRLs and a normal observer performed a fixation stability task. Fixation was tracked monocularly. The low vision observer was calibrated using his primary PRL and instructed to “look at” the 1 º fixation cross with one of his two PRLs. The fixation target flickered when eye position deviated beyond a set tolerance, providing feedback and requiring attention. Practice trials were performed by the normal observer before fixation stability was measured. The normal observer was required to hold their gaze at a 10 º or 15 º to the left of the feedback target, forcing the decoupling of gaze and attention. Fixation stability was computed with the bivariate contour ellipse area (BCEA) for a set of fixations (Bellman, et. al., Opt 2004).
Results: The low vision patient produced an average BCEA value of 1.88 º for his primary PRL. The patient described some difficulty switching to his secondary PRL, and BCEA values were much larger. The normal subject produced average BCEA values of 1.19 and 0.92 for 10 º and 15º respectively. Conclusion: The normally subject achieved better stability with few practice trials as compared to the more experienced low vision subject. This effect may be due to practice with the specific stimulus instead of more extended real-world objects. The increase in stability with eccentricity may reflect a lesser need for attention to detect flickering stimuli in the periphery. Letter or shape discrimination would likely require a more “eccentric” attention, possibly reversing the effect.
This PDF is available to Subscribers Only