Foveal

About: Foveal is a research topic. Over the lifetime, 2652 publications have been published within this topic receiving 94120 citations.

Method and apparatus for low bandwidth transmission of data utilizing of the human eye anatomy

Abstract: A method for the generation of an image on a selectable part of the retina of a viewer's eye (816 and 824), to form an ocular image on the retina (824). The method includes the step of receiving an image being composed of a number of image elements that correspond to the number of cone photoreceptors of a viewer's fovea, so as to constitute a received image. The method further includes the step of displaying the received image so as to constitute a displayed image. The method further includes the step of projecting the displayed image onto a viewer's fovea area, so as to constitute a foveal image (817), such that a number of image elements of the foveal image corresponds to the number of cone photoreceptors of the viewer's fovea. The method further includes the step of projecting said displayed image onto a viewer's retina so as to constitute a retinal image (825).

Simultaneous measurement of two-point-spread functions at different locations across the human fovea

Abstract: An experimental system for measuring simultaneously the retinal images of two-point tests has been developed. In particular we present one experiment in which one of the points is located at the center of the fovea and the other one is at 1 deg of eccentricity. At these two foveal locations the optical image quality is expected to be approximately the same, while the structure of the retina is known to be quite different. Our results of aerial images show small but systematic differences between the two-pointspread functions that are measured at 0 and 1 deg of eccentricity. The image quality is always slightly better in the center of the fovea with the differences more marked in the nasal and inferior orientations. That could be explained by a small but noticeable contribution of the retinal thickness to the optical aberrations of the eye. The possible increment of scattering caused by the increase in retinal thickness at 1 deg was barely measurable in our experiment. An indirect consequence is that retinal reflection has little practical influence on our particular double-pass measurements of the eye's image quality.

Visual acuity in optic atrophy: a quantitative clinicopathological analysis.

Abstract: Analysis of clinicopathological data from 14 eyes with optic atrophy from various causes revealed a simple relationship between visual acuity and the number of surviving axons in the temporal quadrant of the optic nerve head. This provides support for the theory that the minimum angle of resolution (inverse of visual acuity) is directly proportional to the spatial separation of transmitting foveal cones. The theory allows estimation of the functional fraction of foveocortical neural channels from clinical acuity measurements.

Contour interaction in fovea and periphery

Abstract: It has been known for some time that both foveal and peripheral visual acuity are higher for single letters than for letters in a row. Early work showed that this was due to the destructive interaction of adjacent contours (termed contour interaction). It has been assumed to have a neural basis, and a number of competing explanations have been advanced that implicate either high-level or low-level stages of visual processing. Our previous results for foveal vision suggested a much simpler explanation, one determined primarily by the physics of the stimulus rather than the physiology of the visual system. We show that, under conditions of contour interaction or crowding, the most relevant physical spatial-frequency band of the letter is displaced to higher spatial frequencies and that foveal vision tracks this change in spatial scale. In the periphery, however, beyond 5°, the physical explanation is not sufficient. Here we show that there are genuine physiological lateral spatial interactions, which are due to changes in the spatial scale of analysis.

Steady-State VEP and Attentional Visual Processing

Abstract: Publisher Summary Majority of studies that investigated attentional modulation of the visual evoked potential (VEP) have been confined to the transient responses evoked by isolated stimuli. The steady-state visual evoked potential (SSVEP) offers certain advantages. Its signal is easily recorded and quantified and can be rapidly extracted from background noise. Its amplitude to a continuous irrelevant background flicker is attenuated over prefrontal, central, and right parietotemporal regions in the interval following a cue to change the card-sort criterion. Paying attention to a specific region of the visual field is associated with increased amplitudes to stimuli flashed at the attended location. Spatial attention strongly increases the amplitude of the steady-state visual evoked potential. Its phase depends on the transmission time between the stimulus and the evoked brain activity but does not give a direct measure of this transmission time. The pathway originates predominately in the foveal region of the retina from ganglion. This chapter concludes that the SSVEP provides a sensitive measure of spatial attention processes and offers certain advantages over the transient VEP.