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Linh Dang, Laura Walker Renninger, Donald Fletcher; Attention vs. The Eye: Which stabilizes fixation?. Journal of Vision 2010;10(7):502. doi: https://doi.org/10.1167/10.7.502.
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Purpose: Maculopathy patients with a peripheral retinal locus (PRL) for fixation tend to exhibit fixation instability that worsens with PRL eccentricities. Using an artificial scotoma paradigm with normal observers in an orientation discrimination task, we examined the affect of “eccentric attention”, i.e. deviating attention to a PRL (Dang, Renninger & Fletcher, VSS2009). We found the position of the eye in the orbit to be an important factor. In this study, we characterize the relative contribution of gaze and attention deviations to fixation stability and whether it applies to maculopathy patients. Methods: Observers with artificial scotoma performed an orientation discrimination task as a function of eccentricity under three conditions: a) central gaze, eccentric target; b) eccentric gaze, central target; c) eccentric gaze and eccentric target. Maculopathy patients performed a similar task with a) eccentric gaze at the PRL, central target or b) central gaze, eccentric target at the PRL. Results: Artificial scotoma observers experienced a worsening of fixation stability for the eccentric gaze, central target condition as compared to the baseline condition of central gaze, eccentric target. Thus, when the deviation angle of “eccentric attention” is matched, the major cause of eye instability is the position of the eye in the orbit. For zero attentional deviation (eccentric gaze, eccentric target) stability is recovered. Correcting maculopathy patients to use central gaze significantly improved fixation stability. Conclusion: Fixation instability in maculopathy patients may be limited by two factors, 1) the deviation and holding of attention at an eccentric retinal location and 2) the absolute position of the eye in the orbit. If fixation stability is required for an acuity related task, the patient may be able to better stabilize the eye in the center of the orbit by moving their object of regard to an appropriate eccentric location.
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