Academic literature on the topic 'Photoreceptor Spatial Distribution'
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Journal articles on the topic "Photoreceptor Spatial Distribution"
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LITHERLAND, LENORE, SHAUN P. COLLIN, and KERSTIN A. FRITSCHES. "Eye growth in sharks: Ecological implications for changes in retinal topography and visual resolution." Visual Neuroscience 26, no. 4 (July 2009): 397–409. http://dx.doi.org/10.1017/s0952523809990150.
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AbstractThe visual abilities of sharks show substantial interspecific variability. In addition, sharks may change their habitat and feeding strategy throughout life. As the eyes of sharks continue to grow throughout the animal’s lifetime, ontogenetic variability in visual ability may also occur. The topographic analysis of the photoreceptor and ganglion cell distributions can identify visual specializations and assess changes in visual abilities that may occur concurrently with eye growth. This study examines an ontogenetic series of whole-mounted retinas in two elasmobranch species, the sandbar shark, Carcharhinus plumbeus, and the shortspine spurdog, Squalus mitsukurii, to identify regional specializations mediating zones for improved spatial resolution. The study examines retinal morphology and presents data on summation ratios between photoreceptor and ganglion cell layers, anatomically determined peak spatial resolving power, and the angular extent of the visual field. Peak densities of photoreceptors and ganglion cells occur in similar retinal locations. The topographic distribution of neurons in the ganglion cell layer does not differ substantially with eye growth. However, predicted peak spatial resolution increases with eye growth from 4.3 to 8.9 cycles/deg in C. plumbeus and from 5.7 to 7.2 cycles/deg in S. mitsukurii. The topographic distribution of different-sized ganglion cells is also mapped in C. plumbeus, and a population of large ganglion cells (soma area 120–350 μm2) form a narrow horizontal streak across the retinal meridian, while the spatial distribution of ordinary-sized ganglion cells (soma area 30–120 μm2) forms an area in the central retina. Species-specific retinal specializations highlight differences in visually mediated behaviors and foraging strategies between C. plumbeus and S. mitsukurii.
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COLLIN, SHAUN P., NATHAN S. HART, KATE M. WALLACE, JULIA SHAND, and IAN C. POTTER. "Vision in the southern hemisphere lampreyMordacia mordax: Spatial distribution, spectral absorption characteristics, and optical sensitivity of a single class of retinal photoreceptor." Visual Neuroscience 21, no. 5 (September 2004): 765–73. http://dx.doi.org/10.1017/s0952523804215103.
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The dorso-laterally located eyes of the southern hemisphere lampreyMordacia mordax(Agnatha) contain a single morphological type of retinal photoreceptor, which possesses ultrastructural characteristics of both rods and cones. This photoreceptor has a large refractile ellipsosome in the inner segment and a long cylindrical outer segment surrounded by a retinal pigment epithelium that contains two types of tapetal reflectors. The photoreceptors form a hexagonal array and attain their peak density (33,200 receptors/mm2) in the ventro-temporal retina. Using the size and spacing of the photoreceptors and direct measures of aperture size and eye dimensions, the peak spatial resolving power and optical sensitivity are estimated to be 1.7 cycles deg−1(minimum separable angle of 34′7′′) and 0.64 μm2steradian (white light) and 1.38 μm2steradian (preferred wavelength or λmax), respectively. Microspectrophotometry reveals that the visual pigment located within the outer segment is a rhodopsin with a wavelength of maximum absorbance (λmax) at 514 nm. The ellipsosome has very low absorptance (<0.05) across the measured spectrum (350–750 nm) and probably does not act as a spectral filter. In contrast to all other lampreys studied, the optimized receptor packing, the large width of the ellipsosome-bearing inner segment, together with the presence of a retinal tapetum in the photophobicMordacia, all represent adaptations for low light vision and optimizing photon capture.
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DESMOND RAMIREZ, M., DANIEL I. SPEISER, M. SABRINA PANKEY, and TODD H. OAKLEY. "Understanding the dermal light sense in the context of integrative photoreceptor cell biology." Visual Neuroscience 28, no. 4 (July 2011): 265–79. http://dx.doi.org/10.1017/s0952523811000150.
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AbstractWhile the concept of a dermal light sense has existed for over a century, little progress has been made in our understanding of the mechanisms underlying dispersed photoreception and the evolutionary histories of dispersed photoreceptor cells. These cells historically have been difficult to locate and positively identify, but modern molecular techniques, integrated with existing behavioral, morphological, and physiological data, will make cell identification easier and allow us to address questions of mechanism and evolution. With this in mind, we propose a new classification scheme for all photoreceptor cell types based on two axes, cell distribution (aggregated vs. dispersed) and position within neural networks (first order vs. high order). All photoreceptor cells fall within one of four quadrants created by these axes: aggregated/high order, dispersed/high order, aggregated/first order, or dispersed/first order. This new method of organization will help researchers make objective comparisons between different photoreceptor cell types. Using integrative data from four major phyla (Mollusca, Cnidaria, Echinodermata, and Arthropoda), we also provide evidence for three hypotheses for dispersed photoreceptor cell function and evolution. First, aside from echinoderms, we find that animals often use dispersed photoreceptor cells for tasks that do not require spatial vision. Second, although there are both echinoderm and arthropod exceptions, we find that dispersed photoreceptor cells generally lack morphological specializations that either enhance light gathering or aid in the collection of directional information about light. Third, we find that dispersed photoreceptor cells have evolved a number of times in Metazoa and that most dispersed photoreceptor cells have likely evolved through the co-option of existing phototransduction cascades. Our new classification scheme, combined with modern investigative techniques, will help us address these hypotheses in great detail and generate new hypothesis regarding the function and evolution of dispersed photoreceptor cells.
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LITHERLAND, LENORE, and SHAUN P. COLLIN. "Comparative visual function in elasmobranchs: Spatial arrangement and ecological correlates of photoreceptor and ganglion cell distributions." Visual Neuroscience 25, no. 4 (July 2008): 549–61. http://dx.doi.org/10.1017/s0952523808080693.
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AbstractThe topographic analysis of retinal ganglion and photoreceptor cell distributions yields valuable information for assessing the visual capabilities and behavioral ecology of vertebrates. This study examines whole-mounted retinas of four elasmobranch species, the ornate wobbegong, Orectolobus ornatus; the whitetip reef shark, Triaenodon obesus; the epaulette shark, Hemiscyllium ocellatum; and the east Australia shovelnose ray, Aptychotrema rostrata, for regional specializations mediating zones of improved visual ability. These species represent a range of lifestyles: benthic, mid-water, diurnal, and nocturnal. Both photoreceptors (visualized using differential interference contrast optics) and ganglion cells (stained with cresyl violet) in the retina are extensively sampled, and their spatial distribution is found to be nonuniform, exhibiting areae or “visual streaks.” In general, the topographic distributions of both cell populations are in register and match well with respect to the location of regions of high density. However, the location of peaks in rod and cone densities can vary within a retina, indicating that preferential sampling of different regions of the visual field may occur in photopic and scotopic vision. Anatomical measures of the optical limits of resolving power, indicated by intercone spacing, range from 3.8 to 13.1 cycles/deg. Spatial limits of resolving power, calculated from ganglion cell spacing, range from 2.6 to 4.3 cycles/deg. Summation ratios, assessed by direct comparison of cell densities of photoreceptors (input cells) and ganglion cells (output cells), at more than 150 different loci across the retina, show topographic differences in signal convergence (ranging from 25:1 to over 70:1). Species-specific retinal specializations strongly correlate to the habitat and feeding behavior of each species.
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Schraermeyer, Ulrich, Hennig Stieve, and Michael Rack. "Cytochemical Localization of Guanylate and Adenylate Cyclase in Photoreceptor Cells of the Fly." Zeitschrift für Naturforschung C 50, no. 9-10 (October 1, 1995): 695–98. http://dx.doi.org/10.1515/znc-1995-9-1016.
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Abstract In photoreceptor cells of invertebrates light triggers an enzyme cascade in which the phos-phoinositide pathway is crucially involved. Likewise, there is growing evidence of an impor tant role of cyclic nucleotides, too. To localize these enzymes able to catalyze the formation of cGM P and cAMP, the spatial distribution of guanylate cyclase (EC 4.6.1.2) and adenylate cyclase (EC 4.6.1.1) was determined in photoreceptor cells of the fly. In photoreceptor cells of the blowfly (Calliphora erythrocephala), the electron dense reaction product of guanylate cyclase was found within the phototransducing region, the rhabdomeral microvilli and in the mitochondria. Staining was also observed throughout the cytoplasm of the microvilli. With the same cytochemical method, reaction product for adenylate cyclase was found on the tips of the photosensory membrane, and not in the cytoplasm of the rhabdomeral microvilli. The results presented here further argue for an important role of one or possibly two cyclic nucleotides in the photoreceptor cells, and possibly in the process of phototransduction of in vertebrates.
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Seno, Keiji, Yumi Yamahama, and Fumio Hayashi. "Spatial distribution of lipid raft components in the disk membrane of frog rod photoreceptor." Comparative Biochemistry and Physiology Part B: Biochemistry and Molecular Biology 151, no. 4 (December 2008): 458–59. http://dx.doi.org/10.1016/j.cbpb.2008.09.047.
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Mayhew, Terry M. "STEREOLOGY AND SOME STRUCTURAL CORRELATES OF RETINAL AND PHOTORECEPTOR CELL FUNCTION." Image Analysis & Stereology 27, no. 1 (May 3, 2011): 1. http://dx.doi.org/10.5566/ias.v28.p1-10.
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The retina is the part of the eye which detects light, transduces it into nerve impulses and plays a significant role in visual perception. Sensitivity to light is multi-factorial and depends on the properties of photopigment molecules, their synthesis and incorporation into photoreceptor membranes and the neural circuitry between photoreceptor cells, bipolar neurons and ganglion neurons. In addition, it depends on structural factors such as the absolute and relative numbers of different types of photoreceptor neurons, their subcellular morphology, their distribution across the retina and the physical dimensions (especially surface areas) and spatial arrangements of their photoreceptor membranes. At the molecular level, these membranes harbour photosensitive pigment molecules comprising transmembrane glycoproteins (opsins, which vary between photoreceptor cells) and a non-protein chromophore. Phototransduction involves a conformational change in the chromophore and activation of an opsin. A transducer G protein, transducin, lowers levels of cGMP and triggers changes in membrane ion permeability including the closure of Na+ channels. This causes the plasmalemma to become less depolarized and the relative hyperpolarization stimulates ganglion cells whose axons form the optic nerve. Phosducin is a light-regulated phosphoprotein located in inner and outer segments of rod photoreceptor cells. It modulates phototransduction by binding to beta and gamma subunits of transducin. This review briefly illustrates ways in which stereology can contribute to our understanding of these processes by providing quantitative data on photoreceptor number, disk membrane surface area and the subcellular immunolocalisation of key molecules.
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HEMMI, JAN M., and ULRIKE GRÜNERT. "Distribution of photoreceptor types in the retina of a marsupial, the tammar wallaby (Macropus eugenii)." Visual Neuroscience 16, no. 2 (March 1999): 291–302. http://dx.doi.org/10.1017/s0952523899162102.
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Mammalian retinae generally contain low numbers of short-wavelength-sensitive cones (S-cones) and higher numbers of middle- to long-wavelength-sensitive cones (M-cones). Some recent studies found topographic differences between the different photoreceptor types and in some instances between photoreceptors and ganglion cells. To investigate this question further, we constructed topographical maps of the different photoreceptors found in an Australian marsupial, the tammar wallaby. We used two polyclonal antibodies that have been shown to label S-cones (JH455) or M-cones (JH492) in a range of mammals. In the tammar wallaby, the antisera clearly distinguish two cone types. JH455 recognizes a small subset of cones (S-cones) with a density of less than 500 cells/mm2 in the ventral retina. Their density increases towards the dorsal retina to about 1600–2000 cells/mm2. JH492 recognizes all remaining cones (M-cones), but also faintly labels most cone cells recognized by JH455. The distribution of M-cones, unlike that of the S-cones, shows a clear horizontal streak of high cell density through the central retina, just like the ganglion cells. Unlike the ganglion cells, however, the M-cones do not peak in the temporal retina but show a very broad peak (12,000–18,000 cells/mm2) in the central or even slightly nasal retina. Based on our findings, the retina of the tammar can be divided into three distinct regions: firstly, the dorsal retina, which has a low ganglion and low cone cell density but a high percentage of S-cones (30%), is thought to provide good spectral sensitivity; secondly, the central horizontal band of retina, which has a high ganglion and high cone cell density and therefore provides good spatial resolution; and thirdly, the ventral retina, which has a low ganglion cell but high cone cell density with few S-cones (5%) and is therefore thought to have a high contrast sensitivity but low acuity.
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Barua, Arnab, Alireza Beygi, and Haralampos Hatzikirou. "Close to Optimal Cell Sensing Ensures the Robustness of Tissue Differentiation Process: The Avian Photoreceptor Mosaic Case." Entropy 23, no. 7 (July 7, 2021): 867. http://dx.doi.org/10.3390/e23070867.
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The way that progenitor cell fate decisions and the associated environmental sensing are regulated to ensure the robustness of the spatial and temporal order in which cells are generated towards a fully differentiating tissue still remains elusive. Here, we investigate how cells regulate their sensing intensity and radius to guarantee the required thermodynamic robustness of a differentiated tissue. In particular, we are interested in finding the conditions where dedifferentiation at cell level is possible (microscopic reversibility), but tissue maintains its spatial order and differentiation integrity (macroscopic irreversibility). In order to tackle this, we exploit the recently postulated Least microEnvironmental Uncertainty Principle (LEUP) to develop a theory of stochastic thermodynamics for cell differentiation. To assess the predictive and explanatory power of our theory, we challenge it against the avian photoreceptor mosaic data. By calibrating a single parameter, the LEUP can predict the cone color spatial distribution in the avian retina and, at the same time, suggest that such a spatial pattern is associated with quasi-optimal cell sensing. By means of the stochastic thermodynamics formalism, we find out that thermodynamic robustness of differentiated tissues depends on cell metabolism and cell sensing properties. In turn, we calculate the limits of the cell sensing radius that ensure the robustness of differentiated tissue spatial order. Finally, we further constrain our model predictions to the avian photoreceptor mosaic.
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LI, BAOQIN, KELLI McKERNAN, and WEN SHEN. "Spatial and temporal distribution patterns of Na-K-2Cl cotransporter in adult and developing mouse retinas." Visual Neuroscience 25, no. 2 (March 2008): 109–23. http://dx.doi.org/10.1017/s0952523808080164.
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AbstractThe Na-K-2Cl cotransporter (NKCC) is a Cl− uptake transporter that is responsible for maintaining a Cl− equilibrium potential positive to the resting potential in neurons. If NKCC is active, GABA and glycine can depolarize neurons. In view of the abundance of GABAergic and glycinergic synapses in retina, we undertook a series of studies using immunocytochemical techniques to determine the distribution of NKCC in retinas of both developing and adult mice. We found NKCC antibody (T4) labeling present in retinas from wild-type mice, but not in NKCC1-deficient mice, suggesting that the NKCC1 subtype is a major Cl− uptake transporter in mouse retina. Strong labeling of NKCC1 was present in horizontal cells and rod-bipolar dendrites in adult mice. Interestingly, we also found that a diffuse labeling pattern was present in photoreceptor terminals. However, NKCC1 was barely detectable in the inner retina of adult mice. Using an antibody against K-Cl cotransporter 2 (KCC2), we found that KCC2, a transporter that extrudes Cl−, was primarily expressed in the inner retina. The expression of NKCC1 in developing mouse retinas was studied from postnatal day (P) 1 to P21, NKCC1 labeling first appeared in the dendrites of horizontal and rod-bipolar cells as early as P7, followed by photoreceptor terminals between P10-P14; with expression gradually increasing concomitantly with the growth of synaptic terminals and dendrites throughout retinal development. In the inner retina, NKCC1 labeling was initially observed in the inner plexiform layer at P1, but labeling diminished after P5. The developmental increase in NKCC expression only occurred in the outer retina. Our results suggest that the distal synapses and synaptogenesis in mouse retinas undergo a unique process with a high intracellular Cl− presence due to NKCC1 expression.
Dissertations / Theses on the topic "Photoreceptor Spatial Distribution"
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LANARO, MATTEO PAOLO. "TOWARDS A COMPUTATIONAL MODEL OF RETINAL STRUCTURE AND BEHAVIOR." Doctoral thesis, Università degli Studi di Milano, 2020. http://hdl.handle.net/2434/710774.
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Human vision is our most important sensory system, allowing us to perceive our surroundings. It is an extremely complex process that starts with light entering the eye and ends inside of the brain, with most of its mechanisms still to be explained. When we observe a scene, the optics of the eye focus an image on the retina, where light signals are processed and sent all the way to the visual cortex of the brain, enabling our visual sensation.
The progress of retinal research, especially on the topography of photoreceptors, is often tied to the progress of retinal imaging systems. The latest adaptive optics techniques have been essential for the study of the photoreceptors and their spatial characteristics, leading to discoveries that challenge the existing theories on color sensation. The organization of the retina is associated with various perceptive phenomena, some of them are straightforward and strictly related to visual performance like visual acuity or contrast sensitivity, but some of them are more difficult to analyze and test and can be related to the submosaics of the three classes of cone photoreceptors, like how the huge interpersonal differences between the ratio of different cone classes result in negligible differences in color sensation, suggesting the presence of compensation mechanisms in some stage of the visual system.
In this dissertation will be discussed and addressed issues regarding the spatial organization of the photoreceptors in the human retina. A computational model has been developed, organized into a modular pipeline of extensible methods each simulating a different stage of visual processing. It does so by creating a model of spatial distribution of cones inside of a retina, then applying descriptive statistics for each photoreceptor to contribute to the creation of a graphical representation, based on a behavioral model that determines the absorption of photoreceptors. These apparent color stimuli are reconstructed in a representation of the observed scene. The model allows the testing of different parameters regulating the photoreceptor's topography, in order to formulate hypothesis on the perceptual differences arising from variations in spatial organization.
Book chapters on the topic "Photoreceptor Spatial Distribution"
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Bautista-Elivar, Nazario, and Ricardo Cruz-Castillo. "Analysis and Modeling of Polygonality in Retinals Tissue Based on Voronoi Diagram and Delaunay Tessellations." In Eye Diseases - Recent Advances, New Perspectives and Therapeutic Options [Working Title]. IntechOpen, 2022. http://dx.doi.org/10.5772/intechopen.106178.
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Several important properties of biological systems are directly related and even determined by the spatial distribution of their constituent elements. Those elements interact with each other and tend to use space in an optimal way, regarding their specific function and environmental constraints. A detailed methodology, based on Voronoi polygons and Delaunay triangles method employed to extract information on the spatial distribution of cells, is presented. On the other hand, diabetic retinopathy (DR) is defined as microvascular pathology. However, some data have suggested that the retinal photoreceptor (RPs) might be important in the pathogenesis of this ocular disease. In this study, the organization of the PRs in control and diabetic-induced rats was compared, using multiphoton microscopy. The PR mosaic was imaged at different locations in non-stained retinas. Thus, this work investigated the pathological changes in the cellular structures of the retina in the early stages of diabetes in laboratory animals. Of the different proposed tools that are highly reliable to be tested with human retinas, the metrics mean averaged distance and the mean square deviation of the angles are found (P < 0.05).
Conference papers on the topic "Photoreceptor Spatial Distribution"
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Artal, Pablo, and Rafael Navarro. "Image quality and photoreceptor distribution." In Ophthalmic and Visual Optics. Washington, D.C.: Optica Publishing Group, 1991. http://dx.doi.org/10.1364/ovo.1991.tha3.
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The two first stages in the spatial information processing performed by the human visual system are the optics of the eye and the spatial sampling in the photoreceptor mosaic. Recently, we have developed at the Instituto de Optica in Madrid, objective techniques to measure both image quality [1-4] and photoreceptors distribution [5]. In particular, we are able to determine image forming properties of the human eye and to measure cone spacing in the living fovea by using together coherent imaging and digital image processing.
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Morimoto, David, Kathleen M. Keehan, Paul E. Kilbride, and Norman P. Blair. "Retinal Reattachment of the Human Macula Assessed by Imaging Fundus Reflectometry." In Noninvasive Assessment of the Visual System. Washington, D.C.: Optica Publishing Group, 1990. http://dx.doi.org/10.1364/navs.1990.tha4.
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Visual recovery following retinal reattachment surgery may be limited by a number of factors. Detachment of the macula is the most important of these, often yielding poor visual acuity after an anatomic success. Gross morphologic changes giving a poor visual result include macular pucker, cellophane maculopathy, cystoid macular edema, and subretinal fibrosis. Some cases with a normal appearing macula by ophthalmoscopy have reduced visual acuity, and these have been attributed to misalignment of photoreceptors, faulty regeneration of photoreceptors, or RPE atrophy (4,5,6). Histologic animal studies have shown degeneration of photoreceptor outer segments following retinal detachment with gradual regeneration following reattachment (2,8). In this report we use fundus reflectometry in vivo to compare the spatial distribution of the visual pigments, contained in photoreceptor outer segments, in 3 patients following retinal reattachment surgery with 9 controls.
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Curcio, Christine A. "Aging and topography of human photoreceptors." In OSA Annual Meeting. Washington, D.C.: Optica Publishing Group, 1986. http://dx.doi.org/10.1364/oam.1986.wc1.
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Age-related decrements in acuity and contrast sensitivity are only partially explained by the combined effects of pupillary constriction and lens opacification. The notion of a neural origin for these visual deficits remains controversial. Limited quantitative data on photoreceptors in aging suggest disorganization of both rod and cone outer segments, displacement of nuclei, and outright cell loss, particularly in the fovea. The relationship of these phenomena to nonpathological changes in retinal supporting tissues which may impair transport of nutrients across the outer blood–retinal barrier is unclear. The effects of age-related point deletions in the photoreceptor mosaic on spatial sampling characteristics of the retina are unknown. Recent studies of photoreceptor distribution in human retina show that individual variability in foveal cone density is much greater than previously appreciated. The implications of this finding for aging studies are (1) sample size must take into account high variability; (2) anatomical data need to be viewed in relation to functional and clinical data from the same individual; (3) photoreceptor counts alone are probably not sufficiently sensitive to detect age-related cell loss, and some measure of mosaic disorder is likely to be more informative.
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Szlyk, Janet P., William Seiple, Wei Xie, and Gerald A. Fishman. "Symmetry Discrimination in Patients with Retinitis Pigmentosa." In Noninvasive Assessment of the Visual System. Washington, D.C.: Optica Publishing Group, 1993. http://dx.doi.org/10.1364/navs.1993.ntua.2.
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Sloan letters, grating patterns, and bar offsets have been used to assess foveal spatial function. Because of the inherent redundancy of these stimuli and the "filling in" due to perceptual completion processes, these tests may not be sensitive enough to changes in the retinal sampling mosaic. An alternative to these stimuli is a spatially random block pattern which has been used to test symmetry discrimination.1 These block patterns consist of elements of a constant size. The intensity of each element is randomly chosen to be either maximum or minimum, and the subsequent patterns range from those with a symmetrical distribution to those with an asymmetrical distribution (Figure 1). Due to the unpredictable location of each pattern element, and the lack of predictable redundancy, subjects cannot rely on perceptual completion processes to make accurate symmetry judgments. The present report tests whether a symmetry paradigm is useful to assess losses in the retinal sampling mosaic in patients in whom a loss of photoreceptors has been reported (e.g., retinitis pigmentosa [RP]2,3)
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Wandell, Brian A. "Color constancy and color discrimination." In OSA Annual Meeting. Washington, D.C.: Optica Publishing Group, 1985. http://dx.doi.org/10.1364/oam.1985.tuh3.
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I have been studying the implications of the hypothesis that the mechanisms of light adaptation compute an internal representation of the retinal image that discounts the spectral power distribution of the ambient light in order to estimate the surface spectral reflectances of objects in the image. I review two consequences of this hypothesis for color discrimination. First, I describe the formulas for estimating surface spectral reflectances from the photoreceptor quantum absorptions. From these formulas, I derive predictions for color discrimination based on the estimated surface spectral reflectances. The structure of the color discrimination equations based on surface spectral reflectance estimates is essentially the same as MacAdam and Silberstein’s line-element equations. The interpretation of the equations with respect to empirical measures—such as wavelength discrimination and the MacAdam ellipses—is somewhat different. The most important difference arises because the observer’s estimate of the local ambient light spectral power distribution, rather than a central measure of the local quantum catch, is assumed to govern the state of light adaptation. Second, I describe how we are attempting to use the color difference measurement based on estimated surface reflectance to predict color differences in spatially complex displays.