Because our eyes are never at rest, the human visual system has to incorporate methods that transform an ever-changing retinal signal into an acute percept. Theories of visual acuity postulated that fixational eye movements (FEM), small mostly involuntary movements that occur even when we fixate, may enhance fine spatial detail by means of a dynamic sampling process (Ahissar & Arieli,
2012; Arend,
1973; Averill & Weymouth,
1925; Marshall & Talbot,
1942). Classic experiments, limited by the technology available at the time, were unable to support these hypotheses (Kelly,
1979; Riggs, Ratliff, Cornsweet, & Cornsweet,
1953; Tulunay-Keesey,
1960; Tulunay-Keesey,
1982; Tulunay-Keesey & Jones,
1976). Recent work by Rucci, Iovin, Poletti, and Santini (
2007), however, demonstrated benefits of FEM for spatial frequencies as high as 10 cycles/° of visual angle in visual stimuli, attributed to a reshaping of spatiotemporal properties by equalizing or “whitening” spatial energy across the temporal domain (Kuang, Poletti, Victor, & Rucci,
2012; Rucci et al.,
2007). Whereas whitening, or spectral equalization, can account for improvements in perceived contrast of retinal images that are resolvable by the cone mosaic (Rucci & Victor,
2015), its benefit cannot be readily extrapolated to predict an improvement for discrimination of high-contrast retinal images at the acuity limit, where the spacing of individual photoreceptor cells is larger than the smallest features that need to be resolved. Humans can resolve optotypes at the 20/10 acuity level (minimum gap dimension of 0.5 arcmin or 2.5 microns in the human retina; maximum spatial frequency of 60 cycles/°) and beyond (Rossi & Roorda,
2010a), suggesting that spatial resolution is not necessarily capped at the structural sampling limit of the retina (Curcio, Sloan, Kalina, & Hendrickson,
1990). It therefore remains unclear how our everyday visual abilities operate at, and even transcend, such limits especially at the fovea, and whether FEM degrade or enhance this performance.