Research on Ganglion Cell Responses After Laser Exposure of the Retina PDF Download
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Author: Myron L. Wolbarsht
Publisher:
ISBN:
Category :
Languages : en
Pages : 51
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Electrophysiological recordings were made from retinal ganglion cells in the macula (including fovea) of several species of Macaque monkeys. After exposure to high-intensity argon or HeNe lasers both above and below the lesion level, the receptive fields lacked a peripheral portion. This was accompanied by a slight increase in the central portion of the receptive field. Some quite large receptive fields were found around the fovea, often extending through it. The large receptive fields could also extend through the site of a laser lesion. No unsymmetrical changes in the receptive field were seen, even in receptive fields adjacent to, or partially within, a laser lesion site. Histological examination did not show any changes in the retinal organization adjacent to laser lesion even where the ganglion cells had center-only receptive fields. (Author).
Author: Myron L. Wolbarsht
Publisher:
ISBN:
Category :
Languages : en
Pages : 51
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Book Description
Electrophysiological recordings were made from retinal ganglion cells in the macula (including fovea) of several species of Macaque monkeys. After exposure to high-intensity argon or HeNe lasers both above and below the lesion level, the receptive fields lacked a peripheral portion. This was accompanied by a slight increase in the central portion of the receptive field. Some quite large receptive fields were found around the fovea, often extending through it. The large receptive fields could also extend through the site of a laser lesion. No unsymmetrical changes in the receptive field were seen, even in receptive fields adjacent to, or partially within, a laser lesion site. Histological examination did not show any changes in the retinal organization adjacent to laser lesion even where the ganglion cells had center-only receptive fields. (Author).
Author: Randolph D. Glickman
Publisher:
ISBN:
Category :
Languages : en
Pages : 7
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This article is the result of investigations of retinal function following low-level exposures from an Nd:glass laser, using in vivo recordings of ganglion cell activity from the rhesus monkey retina. Time-dependent effects of laser exposures on rhesus monkey retinal ganglion cells were studied with a Q-switched, doubled Nd:glass laser, which produced 20 nsec pulses of 530-nm light, and a continuous-wave (CW) argon laser (514.5 nm), which produced exposures of 0.1-msec to 0.1-sec duration. Ganglion cell activity was recorded in situ by means of an intraocular electrode. Ganglion cells exposed to a single 20-nsec exposure, at a sublesion intensity, produced a 60-90 sec discharge of action potentials and exhibited a 2 log or greater elevation of light threshold, depending on beam size and intensity. At equivalent energy levels, the longer exposures produced the same or slightly weaker effects. This result is not as straightforward as it seems. Submillisecond flashes bleach no more than 50% of the visual pigment because of photoregeneration. The Dowling-Rushton relation predicts that a 50% bleach should produce only a 1.5 log loss of cone sensitivity. Exposures longer than 1 msec should not photoregenerate pigment (ie, more pigment will be bleached for a given exposure intensity). In view of the probable differences in pigment bleaching, it appears that the Q-switched laser light adapts the cells out of proportion to the visual pigment actually bleached-a single-cell analogue of Rushton's 'theta' effect. Keywords: Q-switched lasers, Neodymium lasers, Argon lasers, Electrophysiology, Reprints. (KT).
Author:
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ISBN:
Category :
Languages : en
Pages : 11
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Acute (1-hr, 6-hr) and longer term (24-hr) effects of laser injury on retinal function and cellular responses have been studied in the Great Plains rat snake, Elaphe guttata emoryi. This animal is of interest for vision research because its eye has an all-cone retina. A linear array of 5 thermal lesions was placed in the retina of anesthetized animals, near the area centralis, using a Nd:VO4 laser (532 nm), that delivered 50 mW per lO-msec pulse. Retinal function was assessed with the pattern electroretinogram (PERG), recorded before and after the placement of the lesions. PERGs were elicited with counterphased square-wave gratings, and were analyzed by Fourier analysis. The fate of lesioned cells was assessed by immunohistological staining for the transcription factor, NF-kB (which is activated by ionizing and non-ionizing radiation), as well as for the apoptosis marker, caspase-9. The normal snake PERG had the maximum, real amplitude frequency component, determined by Fourier analysis, at the reversal frequency of the grating (i.e. shifts/sec). In the hour following the lesion-producing laser exposures, the PERG response exhibited frequency doubling, i.e. a new response waveform appeared at twice the reversal frequency. By 24-hr post exposure, many lesioned photoreceptors stained positively for both NF-kB and caspase 9. Because the PERG largely reflects retinal ganglion cell activity, the appearance of frequency doubling in the PERG suggests that complementary (push-pull) inputs to ganglion cells are disrupted by the laser lesions. The immunohistological results indicate that activation of NF- B is not necessarily associated with photoreceptor survival after a laser injury.
Author: Myron L. Wolbarsht
Publisher:
ISBN:
Category :
Languages : en
Pages : 58
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The reports of retinal damage from exposure to short pulse laser energy without any visual perception have been reviewed. A series of experiments has been conducted in cats to test retinal function after such laser exposures using neurophysiological recordings from retinal ganglion cells. The receptive fields of the selected ganglion cells were in the area of laser exposure or immediately adjacent to it. Microsensor monitoring of retinal metabolic stability including pH and O2 levels following laser exposure was also attempted. Vigorous neural responses have been recorded from retinal ganglion cells following suprathreshold lesion producing laser exposures within the Ganglion cell receptive fields, or from nerve fibers at the optic disc. The disc recordings always showed responses from ganglion cells following suprathreshold stimulation levels sufficient to cause retinal lesions within the receptive field or in closely adjacent areas of the retina.
Author: Helga Kolb
Publisher:
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Category :
Languages : en
Pages :
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Author: Myron L. Wolbarsht
Publisher:
ISBN:
Category : Color vision
Languages : en
Pages : 53
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The overall purpose of this research was to investigate a method for demonstrating changes in retinal ganglion-cell function after high-intensity radiation such as from a laser or other monochromatic source in the visible region. These experiments were designed to facilitate understanding functional retinal changes required to produce flash-blindness or permanent damage in human eyes, especially in the macular region which is so important in safety measures. Recordings were made from selected and well-characterized ganglion cells in animal retinas. Changes in receptive-field sensitivities were detected as a result of exposure to high-intensity monochromatic or broad-band light in part or all of the field. The time course of sensitivity recovery was also plotted. These results were then correlated with physiological and psychophysical data already known from other animal and human studies. The specific objective of this study was to delineate means by which ganglion cell responses could be used to evaluate color vision and visual-field loss after laser exposure of the monkey retina. Rabbit and cat retinas were used in developing the experimental techniques required for this evaluation. (Author).
Author: 林瑋源
Publisher: Open Dissertation Press
ISBN: 9781374747081
Category : Medical
Languages : en
Pages : 132
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This dissertation, "Neuroprotection of Low Energy Laser on Retinal Ganglion Cells Survival After Optic Nerve Injury" by 林瑋源, Wai-yuan, Leon, Lam, was obtained from The University of Hong Kong (Pokfulam, Hong Kong) and is being sold pursuant to Creative Commons: Attribution 3.0 Hong Kong License. The content of this dissertation has not been altered in any way. We have altered the formatting in order to facilitate the ease of printing and reading of the dissertation. All rights not granted by the above license are retained by the author. DOI: 10.5353/th_b3122286 Subjects: Retinal ganglion cells Optic nerve - Wounds and injuries Optic nerve - Laser surgery
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Category : Aeronautics
Languages : en
Pages : 784
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Lists citations with abstracts for aerospace related reports obtained from world wide sources and announces documents that have recently been entered into the NASA Scientific and Technical Information Database.
Author: Eamonn Thomas Fahy
Publisher:
ISBN:
Category : Glaucoma
Languages : en
Pages : 227
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Author: Bruce E. Stuck
Publisher:
ISBN:
Category : Medical
Languages : en
Pages : 238
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