Showing papers on "Foveal published in 2001"
TL;DR: Foveal pseudocysts are the first step of full-thickness macular hole formation, but they also may evolve into a lamellar hole, may persist unchanged for months, or may resolve completely as mentioned in this paper.
255 citations
TL;DR: A domain-independent computational model that provides a more rigorous account of eye movements and visual encoding and their interaction with a cognitive processor and how the model accounts for aspects of behavior that simpler models of cognitive and visual processing fail to explain.
218 citations
TL;DR: The results demonstrate that even high‐level visual tasks involving object vision can be performed using the relatively coarse information provided by the peripheral retina.
Abstract: It is generally believed that the acuity of the peripheral visual field is too poor to allow accurate object recognition and, that to be identified, most objects need to be brought into foveal vision by using saccadic eye movements. However, most measures of form vision in the periphery have been done at eccentricities below 10∞ and have used relatively artificial stimuli such as letters, digits and compound Gabor patterns. Little is known about how such data would apply in the case of more naturalistic stimuli. Here humans were required to categorize briefly flashed (28 ms) unmasked photographs of natural scenes (39∞ high, and 26∞ across) on the basis of whether or not they contained an animal. The photographs appeared randomly in nine locations across virtually the entire extent of the horizontal visual field. Accuracy was 93.3% for central vision and decreased almost linearly with increasing eccentricity (89.8% at 13∞, 76.1% at 44.5∞ and 71.2% at 57.5∞). Even at the most extreme eccentricity, where the images were centred at 70.5∞, subjects scored 60.5% correct. No evidence was found for hemispheric specialization. This level of performance was achieved despite the fact that the position of the image was unpredictable, ruling out the use of precued attention to target locations. The results demonstrate that even high-level visual tasks involving object vision can be performed using the relatively coarse information provided by the peripheral retina.
196 citations
TL;DR: It is shown that most peripheral PC cells have red–green modulation sensitivity close to that of foveal PC cells, incompatible with the view that PC pathway cells in peripheral retina make indiscriminate connections with retinal circuits devoted to different spectral types of cone photoreceptors.
Abstract: Visual abilities change over the visual field. For example, our ability to detect movement is better in peripheral vision than in foveal vision, but colour discrimination is markedly worse. The deterioration of colour vision has been attributed to reduced colour specificity in cells of the midget, parvocellular (PC) visual pathway in the peripheral retina. We have measured the colour specificity (red-green chromatic modulation sensitivity) of PC cells at eccentricities between 20 and 50 degrees in the macaque retina. Here we show that most peripheral PC cells have red-green modulation sensitivity close to that of foveal PC cells. This result is incompatible with the view that PC pathway cells in peripheral retina make indiscriminate connections ('random wiring') with retinal circuits devoted to different spectral types of cone photoreceptors. We show that selective cone connections can be maintained by dendritic field anisotropy, consistent with the morphology of PC cell dendritic fields in peripheral retina. Our results also imply that postretinal mechanisms contribute to the psychophysically demonstrated deterioration of colour discrimination in the peripheral visual field.
152 citations
TL;DR: Significant abnormality in the foveal amplitude and thefoveal latency of MERG could be detected in pre-AMD or early AMD eyes as well as their asymptomatic contralateral eyes, suggesting MERG as a sensitive tool in detecting early fovea abnormalities in AMD.
Abstract: AIM—To explore the use of multifocal electroretinograms (MERG) in detecting early changes in age related macular degeneration (AMD).
METHOD—15 pre-AMD or early AMD eyes showing retinal drusen or irregular fundus pigmentation with window defects by fluorescein angiography (FA) and mildly decreased visual acuity were examined and compared with their asymptomatic fellow eyes. 20 age matched normal eyes were included as controls. MERG was recorded by a Veris system (version 3.0) using a 103 hexagon stimulus and 218 second total recording time per eye. The first order kernel was used to calculate amplitudes and latencies in three configurations: the nasal and the temporal areas, the superior and the inferior areas, and six concentric rings centred on the fovea.
RESULTS—There were no significant differences in the amplitudes and the latencies between the different regions (nasal versus temporal and superior versus inferior) of the retina as well as between the different groups of eyes (normal, pre-AMD or early AMD, and the asymptomatic fellow eyes) in each region. Using the concentric configuration, the foveal amplitude of pre-AMD or early AMD eyes was significantly suppressed when compared with the age matched control group and their average latency was longer in the fovea than in outer rings and significantly prolonged when compared with the normal control group. Similar changes in amplitude and latency were also observed in the asymptomatic fellow eyes.
CONCLUSION—Significant abnormality in the foveal amplitude and the foveal latency of MERG could be detected in pre-AMD or early AMD eyes as well as their asymptomatic contralateral eyes, suggesting MERG as a sensitive tool in detecting early foveal abnormalities in AMD.
93 citations
TL;DR: A hybrid system that consists of a combination of a knowledgebased reasoning system with a low-level preprocessing by linear and nonlinear neural operators is developed, intended as a first step towards a complete model of the sensorimotor system of saccadic scene analysis.
Abstract: The perception of an image by a human observer is usually modeled as a parallel process in which all parts of the image are treated more or less equivalently, but in reality the analysis of scenes is a highly selective procedure, in which only a small subset of image locations is processed by the precise and efficient neural machinery of foveal vision. To understand the principles behind this selection of the ‘‘informative’’ regions of images, we have developed a hybrid system that consists of a combination of a knowledgebased reasoning system with a low-level preprocessing by linear and nonlinear neural operators. This hybrid system is intended as a first step towards a complete model of the sensorimotor system of saccadic scene analysis. In the analysis of a scene, the system calculates in each step which eye movement has to be made to reach a maximum of information about the scene. The possible information gain is calculated by means of a parallel strategy which is suitable for adaptive reasoning. The output of the system is a fixation sequence, and finally, a hypothesis about the scene.
88 citations
TL;DR: In this paper, a perceptual explanation was proposed: the eyes overshoot the final position of the target, and because of a foveal bias, the judged position is shifted in the direction of motion.
Abstract: The judged final position of a moving stimulus has been suggested to be shifted in the direction of motion because of mental extrapolation (representational momentum). However, a perceptual explanation is possible: The eyes overshoot the final position of the target, and because of a foveal bias, the judged position is shifted in the direction of motion. To test this hypothesis, the authors replicated previous studies, but instead of having participants indicate where the target vanished, the authors probed participants' perceptual focus by presenting probe stimuli close to the vanishing point. Identification of probes in the direction of target motion was more accurate immediately after target offset than it was with a delay. Another experiment demonstrated that judgments of the final position of a moving target are affected by whether the eyes maintain fixation or follow the target. The results are more consistent with a perceptual explanation than with a memory account.
87 citations
TL;DR: The foveal thicknesses measured using OCT and the scanning RTA in healthy subjects agreed with the previously reported data on foveAL thickness, indicating that both instruments can reproducibly quantitate fveal thickness.
Abstract: PURPOSE To assess the reproducibility of retinal thickness measurements in normal subjects and to compare foveal thickness using optical coherence tomography (OCT) and the scanning retinal thickness analyzer (RTA). METHODS Two examiners performed foveal thickness measurements in 24 eyes of 12 healthy subjects using both OCT and the scanning RTA. Intraclass correlation coefficients (ICC) (intra-examiner and inter-examiner) were calculated for the paired foveal thickness measurements obtained with each instrument. RESULTS The average foveal thicknesses measured with OCT and the scanning RTA were 155.1 +/- 14.9 microm and 107.8 +/- 18.6 microm, respectively. The intra-examiner ICCs from the two sessions using the OCT and the scanning RTA were 0.99 and 0.78 and 0.89 and 0.99, respectively. The inter-examiner ICCs of the OCT and the scanning RTA were 0.99 and 0.99, respectively. There was a significant correlation between the foveal thickness measurements with these two instruments (R2 = 0.629, P < 0.0001). CONCLUSION The foveal thicknesses measured using OCT and the scanning RTA in healthy subjects agreed with the previously reported data on foveal thickness. Both instruments can reproducibly quantitate foveal thickness.
86 citations
TL;DR: Evidence is reviewed that lutein and zeaxanthin could improve human visual performance through both acute optical effects at the site of the retina and by maintaining health and functional integrity ofThe retina and crystalline lens.
80 citations
TL;DR: Contrast sensitivity for face identification was measured as a function of image size and it was found that in periphery information was utilised less efficiently and peripheral inferiority arose completely from lower efficiency, not from increased internal noise.
77 citations
TL;DR: A simulator study is presented that compared the effectiveness of current foveal feedback and two implementations of peripheral visual feedback for keeping pilots informed about un commanded changes in the status of an automated cockpit system, resulting in higher detection rates and faster response times.
Abstract: Breakdowns in human-automation coordination in data-rich, event-driven domains such as aviation can be explained in part by a mismatch between the high degree of autonomy yet low observability of modern technology. To some extent, the latter is the result of an increasing reliance in feedback design on foveal vision--an approach that fails to support pilots in tracking system-induced changes and events in parallel with performing concurrent flight-related tasks. One possible solution to the problem is the distribution of tasks and information across sensory modalities and processing channels. A simulator study is presented that compared the effectiveness of current foveal feedback and two implementations of peripheral visual feedback for keeping pilots informed about uncommanded changes in the status of an automated cockpit system. Both peripheral visual displays resulted in higher detection rates and faster response times, without interfering with the performance of concurrent visual tasks any more than does currently available automation feedback. Potential applications include improved display designs that support effective attention allocation in a variety of complex dynamic environments, such as aviation, process control, and medicine.
TL;DR: Foveal thresholds increased immediately with increasing refractive error, particularly for smaller stimulus sizes, and differences in foveal vs peripheral viewing can be explained by differences in ganglion cell receptive field sizes.
Abstract: . Purpose: Previous studies of optical blur in perimetry have measured the effect of foveal refractive error on peripheral perimetric detection thresholds. Since peripheral refractive error can be significantly different from that of the fovea we wished to remove the ambiguity of previous results by correcting the actual peripheral refractive error first before adding blur.
Methods: We measured detection thresholds in the fovea and at 30 degrees in the horizontal temporal field in two trained observers. Peripheral refractive error was determined at each location and thresholds measured at the same locations for stimuli ranging in size from 0.2 to 6.4 degrees and refractive errors between ±4.00 diopters.
Results: Foveal thresholds increased immediately with increasing refractive error, particularly for smaller stimulus sizes. At 30 degrees, thresholds for smaller stimuli were less affected by defocus initially and then increased more sharply. Larger stimuli were relatively unaffected by defocus such that when stimulus size reached 1.6 degrees there was little or no increase in threshold for refractive error between ±4.00 diopters.
Conclusions: Peripheral refractive error, largely forgotten by perimetrists, has a significant effect on performance, particularly for smaller stimuli. Differences in foveal vs peripheral viewing can be explained by differences in ganglion cell receptive field sizes.
TL;DR: It is claimed that the higher-level cognition involved in word recognition does not completely transcend initial foveal splitting, and a schematic connectionist model of word recognition is presented that instantiates the precise splitting of the visual field and the contralateral projection of the two hemifields.
Abstract: We argue that the projection of the visual field to the cortex constrains and informs the modeling of visual word recognition. On the basis of anatomical and psychological evidence, we claim that the higher-level cognition involved in word recognition does not completely transcend initial foveal splitting. We present a schematic connectionist model of word recognition that instantiates the precise splitting of the visual field and the contralateral projection of the two hemifields. We explore the special nature of the exterior (i.e., first and last) letters of words in reading. The model produces the correct behavior spontaneously and robustly. We analyze this behavior of the model with respect to words and random patterns and conclude that the systematic division of the visual input has predictable, general informational consequences and is chiefly responsible for the exterior letters effect.
TL;DR: A carefully controlled test is reported to examine the influence of training on the resolution thresholds for two lines and on Landolt C acuity measurements in the retinal periphery in eight normal adults.
TL;DR: Multiple regression analysis was used at each viewing distance to predict fixation disparity from dark vergence, dark focus, accommodative gain and accommodative convergence: these accommodative measures had little effect on the inter-individual variability of near fixation disparity nor on the linear slope of fixation disparity as a function viewing distance.
Patent•
13 Apr 2001
TL;DR: In this paper, a foveal reconstruction processor is proposed to reconstruct a signal approximation which has the same geometrical structures as the input signal along the trajectories and which is regular away from these trajectories.
Abstract: Methods and apparatus for processing n-dimensional digitized signals with a foveal processing which constructs a sparse representation by taking advantage of the geometrical regularity of the signal structures. This invention can compress, restore, match and classify signals. Foveal coefficients are computed with one-dimensional inner products along trajectories of an n-directional trajectory list. The invention includes a trajectory finder which computes an n-directional trajectory list from the input n-dimensional signal, in order to choose optimal locations to compute the foveal coefficients. From foveal coefficients, a foveal reconstruction processor recovers a signal approximation which has the same geometrical structures as the input signal along the trajectories and which is regular away from these trajectories. A foveal residue can be calculated as a difference with the input signal. A bandelet processor decorrelates the foveal coefficients by applying invertible linear operators along each trajectory. Bandelet coefficients are inner products between the signal and n-dimensional bandelet vectors elongated along the trajectories. A geometric processor computes geometric coefficients by decorrelating the coordinates of these trajectories with linear operators, to take advantage of their geometrical regularity. Setting to zero small bandelet coefficients and small geometric coefficients yields a sparse signal representation.
TL;DR: The objective of the study was to measure the interactions between visual thresholds for a simple light presented peripherally and a simultaneously performed cognitive task presented foveally and to discuss the known neurophysiological characteristics of the primary visual pathway.
Abstract: The objective of the study was to measure the interactions between visual thresholds for a simple light (the secondary task) presented peripherally and a simultaneously performed cognitive task (the primary task) presented foveally The primary task was highly visible but varied according to its cognitive complexity. Interactions between the tasks were determined by measuring detection thresholds for the peripheral task and accuracy of performance of the foveal task. Effects were measured for 5, 10, 20, and 30 deg eccentricity of the peripherally presented light and for three levels of cognitive complexity. Mesopic conditions (0.5 lx) were used. As expected, the concurrent presentation of the foveal cognitive task reduced peripheral sensitivity. Moreover, performance of the foveal task was adversely affected when conducting the peripheral task. Performance on both tasks was reduced as the level of complexity of the cognitive task increased. There were qualitative differences in task interactions between the central 10 deg and at greater eccentricities. Within 10 deg there was a disproportionate effect of eccentricity, previously interpreted as the 'tunnel-vision' model of visual field narrowing. Interactions outside 10 deg were less affected by eccentricity. These results are discussed in terms of the known neurophysiological characteristics of the primary visual pathway.
TL;DR: It was concluded that the act of concentration to the foveal field or the task requiring attention to theFoveal Field, enhanced the VEP response to foveAL field stimulation and suppressed the V EP to the peripheral field.
Abstract: The effects of foveal field attention on pattern reversal visual evoked potential (VEP) were investigated in thirteen normal subjects. Conventional monocular VEP was recorded during the three conditions of control, foveal concentration and reaction time task. Three patterns of checkerboard, which were full field (radius, 0-9 degrees), peripheral field (2.5-9 degrees) and foveal field (0-2.5 degrees), were presented for the stimulation in each condition. The P100 and N145 amplitude of the peripheral field VEP were significantly smaller during the concentration and the reaction time task conditions than that in the control session, while the foveal field VEP amplitudes were enhanced in the concentration and reaction time tasks conditions. The full field VEP amplitudes were not significantly changed by the conditions. We concluded that the act of concentration to the foveal field or the task requiring attention to the foveal field, enhanced the VEP response to foveal field stimulation and suppressed the VEP to the peripheral field. A gating effect in area V1 was speculated, although extra-striate cortex might contribute.
TL;DR: In this article, trained rhesus monkeys were asked to maintain fixation on isovergence targets at different horizontal eccentricities during 10 Hz oscillations along different horizontal directions, and the two eyes moved in compliance with the geometrical constraints of the gaze-stabilization hypothesis, although response gains were generally small.
Patent•
16 Apr 2001TL;DR: In this paper, a simple optical imaging system with a spatial light modulator located at or near a pupil plane to correct aberrations is presented, where maximum resolution is obtained for a limited region defined by a single fixation point (a foveal region) within the field of view.
Abstract: A foveated imaging system using a relatively simple optical imaging system with a spatial light modulator located at or near a pupil plane to correct aberrations. Maximum resolution is obtained for a limited region defined by a single fixation point (a foveal region) within the field of view. The fixation point can be changed manually, by using a predetermined scan pattern, or automatically varied for surveillance or tracking applications.
TL;DR: Improvement in detection and resolution acuity in peripheral vision implies that the two monocular ganglion cell sampling arrays combine at a higher level resulting in a higher binocular sampling density.
TL;DR: Comparisons of fading times as a function of flicker frequency for the blue scotoma, foveal afterimages and optically stabilized images indicate a common time course, consistent with the hypothesis that perceptual filling-in of the fovea reflects the operation of neural processes similar to those involved in fading and regeneration of stabilized images.
TL;DR: The foveal appendage led development in the periphery, had the greatest innervated surface area in embryos, and developed mature nerve terminals and epidermal sensory organs first; also, in developing cortex, markers for metabolic activity (cytochrome oxidase) appeared first in the fovea representation.
Abstract: Star-nosed moles have 11 mechanosensory appendages surrounding each nostril, and primary afferents from a single appendage—the tactile fovea—are greatly over-represented in somatosensory cortex. It was found that the foveal appendage led development in the periphery, had the greatest innervated surface area in embryos, and developed mature nerve terminals and epidermal sensory organs first; also, in developing cortex, markers for metabolic activity (cytochrome oxidase) appeared first in the fovea representation. This developmental sequence may provide the fovea with an advantage in a competition for cortical space, and account for the much larger areas of cortex devoted to foveal afferents.
TL;DR: Bouton's skink, Cryptoblepharus boutonii africanus, is a small, diurnal lizard living on outcrops along the coast of East Africa under high ambient light intensities and has a pure‐cone retina containing single and double visual cells.
Abstract: Bouton's skink, Cryptoblepharus boutonii africanus, is a small, diurnal lizard living on outcrops along the coast of East Africa under high ambient light intensities. It is characterized by relatively large eyes (maximal diameter about 2 mm), with immovable eyelids forming a transparent spectacle and with a virtually constant pupil diameter. The single fovea in the central retina is well developed, with a clearly defined pit, which is relatively deep but not funnel-shaped. The foveal pit is not devoid of the outer nuclear and outer plexiform layers; only the main part of the inner nuclear layer is displaced laterally, resulting in a pit with gradual sloping towards its edges. Thus, the fovea appears to be concaviclivate, as in the eyes of lacertids, varanids, and gekkonids. The central position of the foveae in these laterally placed scincid eyes corresponds with monocular fixation, e.g., of detected prey. C. boutonii has a pure-cone retina containing single and double visual cells. The latter consist of two cells of unequal sizes. Yellowish oil droplets are present in single cones and the minor members of the double cones in all retinal regions. The visual cells of the different retinal regions do not differ in the ultrastructure of their components but differ considerably in size. The outer segments of the foveal cones are twice as long as those of the peripheral cones. Except for the pedicles, the diameters of the components of the visual cells decrease towards the fovea, resulting in an increase in visual acuity. J. Comp. Neurol. 436:487–496, 2001. © 2001 Wiley-Liss, Inc.
TL;DR: According to the detection model of human spatial vision the MTF of the retina and subsequent neural visual pathways (P(c) is independent of spatial frequency, reflecting the lack of precortical lateral inhibition for equiluminous chromatic stimuli in spatiochromatically opponent retinal ganglion cells and dLGN neurons.
TL;DR: The ADSpeak frequency of the stimulus configuration does not provide an adequate explanation for the foveal crowding effect and several discrepancies between ADS peak frequency predictions and empirical data were shown.
TL;DR: Investigation of the possible role of peripheral vision in the control of orientation and landing balance in a back tuck somersault found gymnasts were less stable at landing when vision was absent as compared to the three other vision conditions.
Abstract: Although vision appears to enhance performance of somersaulting skills, few studies have investigated the source (foveal or ambient) of useful visual cues that can potentially be used by gymnasts d...
Patent•
27 Nov 2001
TL;DR: In this paper, a foveated imaging system using a relatively simple optical imaging system with a reflective spatial light modulator at or near a pupil plane to correct off-axis aberrations.
Abstract: PRS0847A foveated imaging system using a relatively simple optical imaging system with a reflective spatial light modulator at or near a pupil plane to correct off-axis aberrations. Maximum resolution is obtained for a single fixation point (foveal region) within the field of view at a time. The fixation point can be changed manually, by a predetermined scan pattern, or automatically varied for surveillance or tracking applications. A pre-calibrated look up table is used to vary the reflective spatial light modulator for each fixation point.
TL;DR: In this article, the authors measured the threshold contrast for circular, collinear, and orthogonal Gabor stimuli of 6 Hz temporal frequency presented 7 deg above the fixation point and found that threshold contrast energy is minimal for a class of stimuli whose Fourier-spectra bandwidth is less than ∼ 1 octave.
Abstract: Previous studies have specified the foveal pattern that is seen most efficiently, with the assumption that the waveform of the best pattern matches the impulse response of the most sensitive visual filter. We measured the threshold contrast for circular, collinear, and orthogonal Gabor stimuli of 6 Hz temporal frequency presented 7 deg above the fixation point. We found that the threshold contrast energy is minimal for a class of stimuli whose Fourier-spectra bandwidth is less than ∼1 octave. These findings suggest that an energy algorithm might underlie spatial summation of peripheral Gabor patches. The different behavior of spatial summation in fovea and periphery might reflect the differences in pattern detectability across space in the central and peripheral visual fields. It is also possible that a coherent (cross-correlation) algorithm is employed in detection of foveal stimuli and that an incoherent (energy) algorithm is employed in detection of peripheral stimuli.
07 Oct 2001
TL;DR: This work proposes that the look-ahead fixations represent a strategic deployment of attentional and visual resources to optimize information gathering during natural tasks and reveals a novel perceptual strategy, in which objects of future interaction were foveated seconds before the information was "needed" for a task.
Abstract: Visual perception is virtually effortless, operating at a level below conscious experience. Because it most frequently operates without attentive intervention, it does not yield to introspective report. The foveal/peripheral distribution of photoreceptor density in the human eye requires a mechanism to rapidly re-target areas in the environment for visual inspection. The eyes are moved both toward areas where high-acuity, central vision is required and toward objects of interest to the current task. Monitoring those eye movements can provide a window into perception. Subjects' eye movements were monitored while they performed the familiar, complex task of hand-washing. Analysis revealed a novel perceptual strategy, in which objects of future interaction were foveated seconds before the information was "needed" for a task. These lookahead fixations are task-dependent; while they occurred in over 3% of fixations in the hand-washing task, their frequency fell to less than 1% in a control experiment. We propose that the look-ahead fixations represent a strategic deployment of attentional and visual resources to optimize information gathering during natural tasks.