Differential Effects of Short-and Long-Pulsewidth Laser Exposures on Retinal Ganglion Cell Response PDF Download
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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: Randolph D. Glickman
Publisher:
ISBN:
Category :
Languages : en
Pages : 7
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Book Description
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: 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: United States. Congress. House. Committee on Armed Services. Subcommittee on Research and Development
Publisher:
ISBN:
Category : History
Languages : en
Pages : 400
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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:
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ISBN:
Category : Medicine
Languages : en
Pages : 1328
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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:
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ISBN:
Category :
Languages : en
Pages : 26
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A computer program was developed to simulate a pilot's reaction to an ocular exposure from a multiple-pulse laser. The simulation outlines five different scenarios of eye and head responses that are likely to occur in response to a laser exposure. These responses are: 1) closing the eyes; 2) centering the laser image on the fovea with a saccadic eye movement; 3) executing a saccade to avoid foveating the laser beam; 4) holding the eyes stationary relative to the laser beam; and 5) tracking a moving object during the laser exposure. The simulation modeled the effects of a 1-s laser exposure with pulse rates of 5,15, or 30 pulses/s and beam angles of 0, 10, 20, or 30 deg eccentric from the point of fixation. The output of the simulation predicted the number and distribution of lesions in terms of retinal topography and acuity under the aforementioned conditions. The results of the simulation demonstrated that the pilot's reactions significantly influenced the number and pattern of lesions deposited on the retina. The most serious threat to vision resulted from an eye improvement that foveated the laser. Eye movements that diverted the laser from the fovea appeared to minimize the impact on vision. However, further work will be needed to quantify the size and location of athe visual field loss.
Author:
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ISBN:
Category :
Languages : en
Pages : 1058
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Author:
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ISBN:
Category : Science
Languages : en
Pages : 1578
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Author:
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ISBN:
Category : Optical instruments
Languages : en
Pages : 774
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