Changes in human short-wavelength-sensitive and achromatic resolution acuity with retinal eccentricity and meridian

Abstract

Psychophysical measurements using achromatic grating resolution acuity in peripheral vision show a prominent retinal asymmetry in acuity which is consistent with predicted values based on available estimates of midget ganglion cell density. Recent studies have shown that peripheral grating resolution acuity values for short-wavelength-sensitive (SWS) isolating gratings in normal observers are closely related to predicted values based on the underlying small bistratified ganglion cell density. By measuring SWS resolution acuity at different locations across the visual field, we wished to see if any significant acuity asymmetry exists for the short-wavelength system. In addition to this, we wanted to compare SWS and achromatic resolution acuity at different retinal locations of equal eccentricity. SWS and achromatic grating resolution acuity was measured in two observers at a number of different retinal meridians of 10- and 25-deg eccentricity from the fovea, and out to 35-deg eccentricity along the horizontal meridian. Achromatic resolution acuity was higher than SWS resolution acuity at all locations. At 10-deg eccentricity there was slight radial asymmetry in SWS and achromatic acuity, both displaying highest acuity along the horizontal meridian. At 25-deg eccentricity, SWS and achromatic acuity showed significant asymmetry with acuity being higher in the nasal retina compared to the temporal retina and with higher acuity in the superior retina compared to the inferior retina. At 35-deg eccentricity, the acuity asymmetry along the horizontal meridian was maintained with acuity for both significantly higher in the nasal retina. The SWS acuity changes with eccentricity and meridian were qualitatively similar to that found for achromatic acuity at the majority of retinal locations. Like achromatic acuity, SWS acuity shows significant asymmetry at different retinal locations of equal eccentricity. This suggests that both the midget and small bistratified ganglion cell population density changes significantly with retinal location and eccentricity. SWS acuity appears to change in parallel with achromatic acuity for the majority of retinal locations measured, although the amount of nasotemporal asymmetry appears to be slightly less for the SWS system at 25- and 35-deg eccentricity.

Target–object integration, attention distribution, and object orientation interactively modulate object-based selection

“…In correspondence with this theory of an attentional advantage when crossing the vertical versus the horizontal meridian, other research has shown that visual performance is superior across the vertical meridian because discriminability is comparatively enhanced and temporal dynamics are comparatively rapid (although the rate of information accrual may be faster along the disadvantaged meridian; Carrasco et al, 2002). Indeed various studies have shown that visual acuity (Beirne, Zlatkova, & Anderson, 2005;Rovamo, Virsu, Laurinen, & Hyvarinen, 1982) and contrast sensitivity (Carrasco, Evert, Chang, & Katz, 1995;Carrasco, Talgar, & Cameron, 2001;Rijsdijk, Kroon, & van der Wildt, 1980) are better when crossing the vertical versus the horizontal meridian. Importantly, the presence of the meridian effect in object-based attention underscores the importance of including Orientation as a factor when analyzing data, which is surprisingly atypical across studies in this field (e.g., Goldsmith & Yeari, 2003;He, Fan, Zhou, & Chen, 2004;Lamy & Egeth, 2002;Marino & Scholl, 2005;Moore et al, 1998).…”

The Spatial and Temporal Deployment of Voluntary Attention across the Visual Field

“…One of them is that visual acuity is higher along the horizontal than the vertical axis [29]–[31]. However, Beirne et al show that there is no difference between horizontal and vertical acuity for eccentricities of 10°, which corresponds to the eccentricity at which our stimuli are presented in both configurations.…”

Spatial and Temporal Dynamics of Attentional Guidance during Inefficient Visual Search

“…However, current knowledge on visual acuity anisotropies does not support this hypothesis. Indeed, for example, Beirne et al [29], only found very small differences between visual acuity along the horizontal and vertical meridians for an eccentricity of 10° and this difference is probably even smaller at an eccentricity of 4°. Therefore, it is unlikely that the acuity variation could explain the large benefit in detection performance we found for letters located near the horizontal meridian.…”