Topic
Foveal
About: Foveal is a research topic. Over the lifetime, 2652 publications have been published within this topic receiving 94120 citations.
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01 Jan 1998
TL;DR: Thresholds were measured for five tasks: line detection, intensity discrimination, two-line resolution, vernier acuity and line-orientation discrimination, finding the classical oblique effect is consistently found only in orientation discrimination.
48 citations
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TL;DR: For instance, the authors found that fixation times on a foveal target word were shorter when the target was accompanied by an orthographically similar parafoveal word than when the parallel word was dissimilar, and that the size of the effect tended to vary with both the relative frequency of target and parallel words, and the position of the critical letter.
Abstract: One of the main controversies in the field of eye movements in reading concerns the question of whether the processing of two adjacent words in reading occurs in sequence, or in parallel. To distinguish between these views, the present experiment tested the presence of parafoveal‐on‐foveal effects with pairs of orthographically related words (or neighbours that differed by a single letter) in a controlled but reading‐like situation. Results revealed that fixation times on a foveal target word were shorter when the target was accompanied by an orthographically similar parafoveal word than when the parafoveal word was dissimilar. Furthermore, the size of the effect tended to vary with both the relative frequency of target and parafoveal words, and the position of the critical letter. These results were interpreted in the framework of a pure parallel processing hypothesis, where the processing of adjacent words is only limited by visual acuity, and the respective lexical properties of the foveal and parafove...
48 citations
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TL;DR: The definite clinical value of contrast sensitivity measurements is that they can identify incipient abnormalities in the visual pathways that subserve foveal vision, and using sinusoidal gratings as stimuli for both contrast sensitivity and for VEP measurements is useful in a research-oriented clinical testing facility.
Abstract: In this chapter the theoretical reasons were outlined and clinical data summarized as to why spatial contrast measurements can reveal visual losses that are not uncovered by testing visual acuity, no matter which optotype one uses or how carefully the measurement is made. Spatial contrast sensitivity measurements may disclose different types of contrast losses in patients with different lesions but with identical visual acuity. The relationship of different types of spatial contrast sensitivity losses (plotted as visuograms) to specific location or cause of lesions is not yet clear. Patients with glaucoma show losses that occur infrequently in other types of eye or visual pathway diseases, but the specificity of the typical contrast loss needs confirmation. The definite clinical value of contrast sensitivity measurements is that they can identify incipient abnormalities in the visual pathways that subserve foveal vision. In addition to this definite diagnostic application, using sinusoidal gratings as stimuli for both contrast sensitivity and for VEP measurements is useful in a research-oriented clinical testing facility.
48 citations
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TL;DR: The pipefish possesses a deep, pit fovea which, although lacking the displacement of the inner retinal layers as described in other vertebrate foveae, is characterised by the exclusion of rods, a marked increase in the density of photoreceptors and a regular square mosaic of four double cones surrounding a central single cone.
Abstract: The foveal and non-foveal retinal regions of the pipefish, Corythoichthyes paxtoni (Syngnathidae, Teleostei) are examined at the level of the light and electron microscopes The pipefish possesses a deep, pit (convexiclivate) fovea which, although lacking the displacement of the inner retinal layers as described in other vertebrate foveae, is characterised by the exclusion of rods, a marked increase in the density of photoreceptors and a regular square mosaic of four double cones surrounding a central single cone In the perifoveal and peripheral retinal regions, the photoreceptor mosaic is disrupted by the insertion of large numbers of rods, which reduce spatial resolving power but may uniformly increase sensitivity for off-axis rays In addition to a temporal fovea subtending the frontal binocular field, there is also a central area centralis subtending the monocular visual field Based on morphological comparisons with other foveate teleosts, four foveal types are characterised and foveal function discussed with respect to the theoretical advantage of a regular square mosaic
48 citations
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TL;DR: An imaging model is described that examines the smallest cone photoreceptors in the fovea of normal human subjects and analyze how different factors contribute to their resolution, which includes basic optical factors such as wavelength and pupil size.
Abstract: To better understand the limitations of high-resolution adaptive optics scanning laser ophthalmoscopy (AOSLO), we describe an imaging model that examines the smallest cone photoreceptors in the fovea of normal human subjects and analyze how different factors contribute to their resolution. The model includes basic optical factors such as wavelength and pupil size, and defines limits caused by source coherence which are specific to the AOSLO imaging modality as well as foveal cone structure. The details of the model, its implications for imaging, and potential techniques to circumvent the limitations are discussed in this paper.
48 citations