Variations in sensory eye dominance along the horizontal meridian.

Sensory eye dominance refers to the dominance of one eye's input over the other during interocular conflict, such that, when discrepant images are presented dichoptically, one eye's image will dominate perception. This study focuses on how sensory eye dominance varies across visual space. Although some characteristics of variations in sensory eye dominance across visual space have been described before, results so far are largely conflicting. Here I argue that this conflict is caused by the fact that different studies used different methods to assess sensory eye dominance, combined with using a wide range of eccentricities. To systematically and continuously describe sensory eye dominance across the visual field, I used a novel method-tracking Continuous Flash Suppression-in which a visual target presented to a single eye moved across the horizontal meridian while being in constant competition with a dynamic mask presented to the other eye. Eye dominance across the visual field could be described and quantified using three factors: (1) a generic preference for the nasal visual field in combination with (2) an observer-dependent general bias for using the left, right, or neither eye. On top of these, some observers had (3) idiosyncratic biases in local sensory eye dominance. I argue that, while idiosynchratic local biases within an observer probably stem from optical, retinal, or cortical imbalances, the observed nasal advantage is functional: it allows to bias the interocular competition to fixated, partly occluded distant objects of interest.