When looking at the world monocularly, we do not perceive that there is a blind spot in the visual field corresponding to the optic disc, the region of the retina where there are no photoreceptors. In contrast, we perceive edges and patterns of surfaces as if were detected by photoreceptors. This phenomenon is called filling-in. To investigate whether the filling-in distorts space perception, thirty adults had their right eye blind spots mapped and they compared the length of two horizontal bars under right monocular viewing condition. The results point out a lateral asymmetry in the central visual field of the right eye in length comparisons and that the filling-in effect at the blind spot does not distort visual space perception.
Filling-in; Blind spot; Linear size perception; Psychophysics; PEST
