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Ganglion Cell Density (ganglion + cell_density)

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Life Sciences55%

Selected Abstracts

Scaling the structure,function relationship for clinical perimetry

ACTA OPHTHALMOLOGICA, Issue 4 2005
Ronald S. Harwerth
Abstract. Purpose:,The full ranges of glaucomatous visual field defects and retinal ganglion cell losses extend over several orders of magnitude and therefore an interpretation of the structure,function relationship for clinical perimetry requires scaling of both variables. However, the most appropriate scale has not been determined. The present study was undertaken to compare linear and logarithmic transformations, which have been proposed for correlating the perimetric defects and neural losses of glaucoma. Methods:,Perimetry, by behavioural testing, and retinal histology data were obtained from rhesus monkeys with significant visual field defects caused by experimental glaucoma. Ganglion cell densities were measured in histologic sections of retina that corresponded to specific perimetry test locations for the treated and control eyes. The linear (percentage) and logarithmic (decibel) relationships for sensitivity loss as a function of ganglion cell loss were analysed. Results:,With decibel scaling, visual sensitivity losses and ganglion cell densities were linearly correlated with high coefficients of determination (r2), although the parameters of the functions varied with eccentricity. The structure,function relationships expressed as linear percentage-loss functions were less systematic in two respects. Firstly, the relationship exhibited considerable scatter in the data for small losses in visual sensitivity and, secondly, visual sensitivity losses became saturated with larger losses in ganglion cell density. The parameters of the percentage-loss functions also varied with eccentricity, but the variation was less than for the decibel-loss functions. Conclusions:,Linear scaling of perimetric defects and ganglion cell losses might potentially improve the structure,function relationship for visual defects associated with small amounts of cell loss, but the usefulness of the relationship is limited because of the high variability in that range. With log,log co-ordinates, the structure,function relationship for clinical perimetry is relatively more accurate and precise for cell losses greater than about 3 dB. The comparatively greater accuracy and precision of decibel loss functions are a likely consequence of the logarithmic scale of stimulus intensities for perimetry measurements and because the relationship between visual sensitivity and the number of neural detectors is a form of probability summation. [source]

Regional specialization of the Ganglion cell density in the retina of the Ostrich (Struthio camelus)

ANIMAL SCIENCE JOURNAL, Issue 1 2010
Mohammad L. RAHMAN
ABSTRACT In this study, retinal whole-mount specimens were prepared and stained with 0.1% cresyl violet for the ganglion cell study in the Ostrich (Struthio camelus). The total number, distribution, and size of these cells were determined in different retinal regions. The mean total number of ganglion cells (three retinas) was 1 435 052 with an average density of 652 cells/mm2. The temporo , nasal area of the retina with high cell density were identified with the peak of 7525 cells/mm2 in the central area. The size of most ganglion cells ranged from 113,403 µm2, with smaller cells predominating along the temporo-nasal streak above the optic disc and larger cells comprising more of the peripheral regions. The average thickness of the retina was 196 µm. The central area was the thickest area (268.6 µm), whereas the peripheral area was the thinnest area. Thus, the specialization of ganglion cell densities, their sizes and the thickness of the retina support the notion that the conduction of visual information towards the brain from all regions of the retina is not uniform, and suggests that the temporo , nasal streak is the fine quality area for vision in ostriches. [source]

Photoreceptor and ganglion cell topographies correlate with information convergence and high acuity regions in the adult pigeon (Columba livia) retina

THE JOURNAL OF COMPARATIVE NEUROLOGY, Issue 5 2009
Angeliza Querubin
Abstract The fovea and area dorsalis are high acuity vision regions in the pigeon retina. However, the degree of neural convergence (an important determinant of acuity) has not been quantified consistently in this bird. The purpose of the study was to determine the topographic density changes and degree of photoreceptor to ganglion cell convergence in the fovea and the area dorsalis. Total photoreceptor and ganglion cell densities were calculated on the horizontal and vertical meridia. In four eyes, retinal topography was mapped for photoreceptors and ganglion cells. Rod density was quantified by counting anti-rod opsin-stained outer segments across the retina. The ratio of cone photoreceptors to ganglion cells, a rough measure of information convergence, was calculated. The fovea and the red field contained significantly higher mean cone and ganglion cell densities compared with the yellow field. Rods were missing from the fovea. Outside the fovea, rods comprised 20% of the photoreceptor population, with no significant density changes across the retina. The ratio of photoreceptors to ganglion cells was highest in the yellow field, suggesting a high degree of information convergence and low acuity. Our data indicate that convergence of cones onto ganglion cells in the red field is similar to that observed in the fovea. Convergence ratios in both the fovea and red field suggest greater visual acuity compared to that of the surrounding yellow field, which is consistent with the higher visual acuities that have been reported in these regions. J. Comp. Neurol. 517:711,722, 2009. © 2009 Wiley-Liss, Inc. [source]

Regional specialization of the Ganglion cell density in the retina of the Ostrich (Struthio camelus)

ANIMAL SCIENCE JOURNAL, Issue 1 2010
Mohammad L. RAHMAN
ABSTRACT In this study, retinal whole-mount specimens were prepared and stained with 0.1% cresyl violet for the ganglion cell study in the Ostrich (Struthio camelus). The total number, distribution, and size of these cells were determined in different retinal regions. The mean total number of ganglion cells (three retinas) was 1 435 052 with an average density of 652 cells/mm2. The temporo , nasal area of the retina with high cell density were identified with the peak of 7525 cells/mm2 in the central area. The size of most ganglion cells ranged from 113,403 µm2, with smaller cells predominating along the temporo-nasal streak above the optic disc and larger cells comprising more of the peripheral regions. The average thickness of the retina was 196 µm. The central area was the thickest area (268.6 µm), whereas the peripheral area was the thinnest area. Thus, the specialization of ganglion cell densities, their sizes and the thickness of the retina support the notion that the conduction of visual information towards the brain from all regions of the retina is not uniform, and suggests that the temporo , nasal streak is the fine quality area for vision in ostriches. [source]

Scaling the structure,function relationship for clinical perimetry

ACTA OPHTHALMOLOGICA, Issue 4 2005
Ronald S. Harwerth
Abstract. Purpose:,The full ranges of glaucomatous visual field defects and retinal ganglion cell losses extend over several orders of magnitude and therefore an interpretation of the structure,function relationship for clinical perimetry requires scaling of both variables. However, the most appropriate scale has not been determined. The present study was undertaken to compare linear and logarithmic transformations, which have been proposed for correlating the perimetric defects and neural losses of glaucoma. Methods:,Perimetry, by behavioural testing, and retinal histology data were obtained from rhesus monkeys with significant visual field defects caused by experimental glaucoma. Ganglion cell densities were measured in histologic sections of retina that corresponded to specific perimetry test locations for the treated and control eyes. The linear (percentage) and logarithmic (decibel) relationships for sensitivity loss as a function of ganglion cell loss were analysed. Results:,With decibel scaling, visual sensitivity losses and ganglion cell densities were linearly correlated with high coefficients of determination (r2), although the parameters of the functions varied with eccentricity. The structure,function relationships expressed as linear percentage-loss functions were less systematic in two respects. Firstly, the relationship exhibited considerable scatter in the data for small losses in visual sensitivity and, secondly, visual sensitivity losses became saturated with larger losses in ganglion cell density. The parameters of the percentage-loss functions also varied with eccentricity, but the variation was less than for the decibel-loss functions. Conclusions:,Linear scaling of perimetric defects and ganglion cell losses might potentially improve the structure,function relationship for visual defects associated with small amounts of cell loss, but the usefulness of the relationship is limited because of the high variability in that range. With log,log co-ordinates, the structure,function relationship for clinical perimetry is relatively more accurate and precise for cell losses greater than about 3 dB. The comparatively greater accuracy and precision of decibel loss functions are a likely consequence of the logarithmic scale of stimulus intensities for perimetry measurements and because the relationship between visual sensitivity and the number of neural detectors is a form of probability summation. [source]

Visual acuity in the cathemeral strepsirrhine Eulemur macaco flavifrons

AMERICAN JOURNAL OF PRIMATOLOGY, Issue 4 2009
Carrie C. Veilleux
Abstract Studies of visual acuity in primates have shown that diurnal haplorhines have higher acuity (30,75 cycles per degree (c/deg)) than most other mammals. However, relatively little is known about visual acuity in non-haplorhine primates, and published estimates are only available for four strepsirrhine genera (Microcebus, Otolemur, Galago, and Lemur). We present here the first measurements of visual acuity in a cathemeral strepsirrhine species, the blue-eyed black lemur (Eulemur macaco flavifrons). Acuity in two subjects, a 3-year-old male and a 16-year-old female, was assessed behaviorally using a two-alternative forced choice discrimination task. Visual stimuli consisted of high contrast square wave gratings of seven spatial frequencies. Acuity threshold was determined using a 70% correct response criterion. Results indicate a maximum visual acuity of 5.1,c/deg for the female (1718 trials) and 3.8,c/deg for the male (846 trials). These values for E. macaco are slightly lower than those reported for diurnal Lemur catta, and are generally comparable to those reported for nocturnal Microcebus murinus and Otolemur crassicaudatus. To examine ecological sources of variation in primate visual acuity, we also calculated maximum theoretical acuity for Cheirogaleus medius (2.8,c/deg) and Tarsius syrichta (8.9,c/deg) using published data on retinal ganglion cell density and eye morphology. These data suggest that visual acuity in primates may be influenced by activity pattern, diet, and phylogenetic history. In particular, the relatively high acuity of T. syrichta and Galago senegalensis suggests that visual predation may be an important selective factor favoring high visual acuity in primates. Am. J. Primatol. 71:343,352, 2009. © 2009 Wiley-Liss, Inc. [source]

The Distribution of Ganglion Cells in the Equine Retina and its Relationship to Skull Morphology

ANATOMIA, HISTOLOGIA, EMBRYOLOGIA, Issue 2 2007
K. E. Evans
Summary It has recently been reported that a strong correlation exists between the distribution of retinal ganglion cells and nose length in the domestic dog. To determine if this phenomenon occurs in another domestic species with diverse skull morphology, the current study examined the distribution of retinal ganglion cells in 30 horses from a variety of breeds. There was a significant variation in the density of ganglion cells found across the retinae. Breed was a significant predictor for ganglion cell density within the visual streak. A strong positive correlation exists between the density of ganglion cells in the visual streak and nasal length. Significant variation was also seen in the area centralis but did not correlate with any of the recorded skull measurements. The findings of this study provide us with further understanding of the equine visual system and the level of variation that exists between individuals of the same species. [source]

The effect of ginkgo biloba on the rat retinal ganglion cell survival in the optic nerve crush model

ACTA OPHTHALMOLOGICA, Issue 5 2010
Ke Ma
Abstract. Purpose:, To investigate the effect of ginkgo biloba on the retinal ganglion cell survival in a rat optic nerve crush model. Methods:, Twenty-four Sprague,Dawley rats were divided randomly into a study group of 12 animals receiving intraperitoneal injections of ginkgo biloba and a control group of 12 animals receiving intraperitoneal saline injections. All injections were performed 1 hr before the optic nerve crush and daily afterwards. For each animal, the right optic nerve was crushed closely behind the globe for 60 seconds using a microclip with 40 g power. The left optic nerve was kept intact. At 23 days after the optic nerve crush, the retinal ganglion cells were labelled retrogradely by injecting 3% fluorogold into both sides of the superior colliculus of the brain. At 4 weeks after the optic nerve crush, the animals were killed. Photographs taken from retinal flat mounts were assessed for the number and density of the retinal ganglion cells. Results:, The survival rate, defined as the ratio of the retinal ganglion cell density in the right eye with the optic nerve crush divided by the retinal ganglion cell density in left eye without an optic nerve trauma, was significantly (p = 0.035) higher in the study group with ginkgo biloba than in the control group (60.0 ± 6.0% versus 53.5 ± 8.0%). Conclusion:, The results suggest that intraperitoneal injections of a ginkgo biloba extract given prior to and daily after an experimental and standardized optic nerve crush in rats were associated with a higher survival rate of retinal ganglion cells. [source]

Scaling the structure,function relationship for clinical perimetry

ACTA OPHTHALMOLOGICA, Issue 4 2005
Ronald S. Harwerth
Abstract. Purpose:,The full ranges of glaucomatous visual field defects and retinal ganglion cell losses extend over several orders of magnitude and therefore an interpretation of the structure,function relationship for clinical perimetry requires scaling of both variables. However, the most appropriate scale has not been determined. The present study was undertaken to compare linear and logarithmic transformations, which have been proposed for correlating the perimetric defects and neural losses of glaucoma. Methods:,Perimetry, by behavioural testing, and retinal histology data were obtained from rhesus monkeys with significant visual field defects caused by experimental glaucoma. Ganglion cell densities were measured in histologic sections of retina that corresponded to specific perimetry test locations for the treated and control eyes. The linear (percentage) and logarithmic (decibel) relationships for sensitivity loss as a function of ganglion cell loss were analysed. Results:,With decibel scaling, visual sensitivity losses and ganglion cell densities were linearly correlated with high coefficients of determination (r2), although the parameters of the functions varied with eccentricity. The structure,function relationships expressed as linear percentage-loss functions were less systematic in two respects. Firstly, the relationship exhibited considerable scatter in the data for small losses in visual sensitivity and, secondly, visual sensitivity losses became saturated with larger losses in ganglion cell density. The parameters of the percentage-loss functions also varied with eccentricity, but the variation was less than for the decibel-loss functions. Conclusions:,Linear scaling of perimetric defects and ganglion cell losses might potentially improve the structure,function relationship for visual defects associated with small amounts of cell loss, but the usefulness of the relationship is limited because of the high variability in that range. With log,log co-ordinates, the structure,function relationship for clinical perimetry is relatively more accurate and precise for cell losses greater than about 3 dB. The comparatively greater accuracy and precision of decibel loss functions are a likely consequence of the logarithmic scale of stimulus intensities for perimetry measurements and because the relationship between visual sensitivity and the number of neural detectors is a form of probability summation. [source]