Topic
Foveal
About: Foveal is a research topic. Over the lifetime, 2652 publications have been published within this topic receiving 94120 citations.
Papers published on a yearly basis
Papers
More filters
TL;DR: The results suggest that current models of eccentricity scaling of contrast sensitivity be re-evaluated to take account of the extensive aliasing zone of spatial frequencies which becomes functional in peripheral vision when the retinal image is well focused.
152 citations
TL;DR: A method for determining retinal foveal position based on normal fixation position relative to the optic disk and the shape of the PRL, characterized by the ratio of PRL ellipse major to minor axis, was found to depend on whether thePRL was vertically or horizontally aligned with the foveAL fixation centroid.
Abstract: Purpose It is difficult to determine the position of a preferred retinal locus (PRL) relative to the fovea in scanning laser ophthalmoscope (SLO) images as a result of disease-related retinal morphologic changes that obscure the fovea. To overcome this problem, we developed a method for determining retinal foveal position based on normal fixation position relative to the optic disk. The normal foveal position measurements can then be used to estimate the distance between a PRL and the fovea. Methods Using the SLO, foveal position was determined for 50 normal subjects by measuring the retinal locus of fixation relative to the optic disk in undistorted SLO images. The resulting normal foveal fixation area is described by a bivariate normal ellipse that can be plotted on any undistorted SLO image. Measurement reliability was assessed by repeated measurements. The PRL relative to the normal foveal fixation area was determined for 24 subjects with macular degeneration and bilateral central scotomas. Results The normal foveal fixation area based on all 50 subjects is described by a p = 0.9 bivariate ellipse whose centroid is located 12.6 degrees temporal to the temporal optic disk edge and 1.4 degrees inferior to a horizontal line bisecting the disk. PRL area is shown to increase with distance from the foveal fixation ellipse centroid. The shape of the PRL, characterized by the ratio of PRL ellipse major to minor axis, was found to depend on whether the PRL was vertically or horizontally aligned with the foveal fixation centroid. Conclusions PRL position relative to the fovea can be reliably estimated by plotting the normal foveal fixation bivariate ellipse on undistorted SLO images of retinas in which the fovea is obscured as a result of the disease process.
151 citations
TL;DR: Much of the research using dynamic display changes has focused on perceptual aspects of the reading process, but it remains unclear as to whether saccades are executed to traverse a certain amount of visual angle or a certain number of letters.
Abstract: Recently there has been a considerable amount of research involving the use of eye movements to study the reading process (Rayner, 1978). This trend is similar to another large-scale research effort undertaken a number of years ago that also dealt with eye movements and reading (Huey, 1908; Tinker, 1958, 1963; Woodworth, 1938). One difference between the earlier research and the more current work is that more sophisticated equipment is now used and display changes contingent upon the position of the eye can be made (McConkie & Rayner, 1975; O'Regan, 1980; Rayner, 1975). Much of the research using dynamic display changes has focused on perceptual aspects of the reading process. Despite this widespread activity, it is still the case that a rather elementary aspect concerning visual factors has not been adequately resolved. That is, it remains unclear as to whether saccades are executed to traverse a certain amount of visual angle or a certain number of letters. For example, eye movements in reading might average around 2 deg of visual angle (Rayner, 1978) because they serve the purpose of bringing text into foveal vision for detailed analysis. If saccades are determined by a critical visual angle, then when viewing distance is decreased (or if the letters are larger) and fewer characters fall within the fovea, the number of characters per saccade will decrease. On the other hand, larger letters or closer viewing distances might allow the letters to be perceived farther out in extrafoveal vision. Is so, readers might execute saccades of a greater visual angle in order to cover a desired number of characters. If either of these alternatives is correct, measures of saccade length in one metric (either visual angle or character spaces) will remain constant as letter size or viewing distance is altered (both change the size of the retinal image, hence the number of letters falling within the fovea), while measures in the other metric will change drastically as retinal image size changes. Huey (1908) and O'Regan (1980) have addressed
151 citations
TL;DR: Results suggest a functioning geniculoextrastriate visual pathway that bypasses V1 and can process orientation and color in the absence of conscious awareness.
Abstract: In humans, the primary visual cortex (V1) is essential for conscious vision. However, even without V1 and in the absence of awareness, some preserved ability to accurately respond to visual inputs has been demonstrated, a phenomenon referred to as blindsight. We used transcranial magnetic stimulation (TMS) to deactivate V1, producing transient blindness for visual targets presented in a foveal, TMS-induced scotoma. Despite unawareness of these targets, performance on forced choice discrimination tasks for orientation (experiment 1) and color (experiment 2) were both significantly above chance. In addition to demonstrating that TMS can be successfully used to induce blindsight within a normal population, these results suggest a functioning geniculoextrastriate visual pathway that bypasses V1 and can process orientation and color in the absence of conscious awareness.
151 citations
Patent•
23 May 2016
TL;DR: In this paper, a system and method for using a virtual reality or augmented reality environment for the measurement and/or improvement of human vestibulo-ocular performance can be implemented by combining a video camera based eye orientation sensor, a head orientation sensor and a display, and an electronic circuit that connects the eye sensor, head sensor, and display.
Abstract: A system and method for using a virtual reality or an augmented reality environment for the measurement and/or improvement of human vestibulo-ocular performance can be implemented by combining a video camera based eye orientation sensor, a head orientation sensor, a display, and an electronic circuit that connects the eye sensor, head sensor, and display. The system and method can be operated in the range of frequencies between 0.01 Hertz and 15 Hertz. The system and method can use a Fourier transform to compute a gain and a phase. The system and method can be used for measuring vestibulo-ocular reflex, dynamic visual acuity, dynamic visual stability, kinetic visual acuity, retinal image stability, or foveal fixation stability in a non-clinical setting. The system and method can be completely portable, head-worn, and self-contained.
150 citations