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Proceedings Paper

Retinal damage following exposure to single pulses of Nd:YAG laser radiation in rabbits and its relation to energy levels
Author(s): T. Kadar; David Peri; J. Turetz; Noam Sapiens; E. Fishbine; R. Sahar; I. Egoz; R. Brandeis
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Paper Abstract

Purpose: The aim of the present study was to characterize permissible exposure limits (MPE) for safety analysis, with an emphasis on the immediate retinal damage following SHG of Nd:YAG Q-Switched laser radiation and to test its correlation to physical parameters. Methods: Pigmented rabbits (n=14) were exposed to single pulses of Nd:YAG laser radiation (532nm, pulse duration:8-12ns) in various energies ranging from 10 to 150 μJ. Exposures were conducted in retina tissue, very close to the optic nerve, with a total of 20 exposures per retina. Retinas were viewed during the first 15 min following exposure, using an on-line digital video camera. Thereafter, animals were sacrificed for histological evaluation. A quantitative analysis of the clinical findings, based on a severity score scale and a morphometric analysis of the extent of the lesions, was used to test the relationship with the laser energy. In addition, hemorrhage thresholds were computed using Probit Analysis. Results: Retinal damage, at various levels of severity, was observed immediately after exposure to energies above 26 μJ, characterized by edema and sub-retinal hemorrhages. The appearance and severity of the lesions varied among animals, between fellow eyes and even within the same retina. The ED50 for immediate pre-retinal hemorrhage was determined as 83μJ and the lesions’ diameter ranged from 141-640μ. A significant correlation (R=0.80, P<0.0001) was found between the extent of the lesions and energy levels. The diameter of the lesions showed a linear (P<0.008) increase with the laser energy. The histological observations indicated elevation of retinal layers and extensive damage in the outer segment of the photoreceptors and in the pigmented epithelial cells layer. Conclusions: A linear, laser-retinal tissue interaction was found immediately following exposure to single pulses of Nd:YAG laser radiation. It is suggested that unlike argon laser, which produces a thermal burn to the eye, Nd:YAG laser damage is a result of a combination of photo-mechanical and thermal mechanism.

Paper Details

Date Published: 1 July 2004
PDF: 9 pages
Proc. SPIE 5319, Laser Interaction with Tissue and Cells XV, (1 July 2004); doi: 10.1117/12.558526
Show Author Affiliations
T. Kadar, Israel Institute for Biological Research (Israel)
David Peri, Israel Institute for Biological Research (Israel)
J. Turetz, Israel Institute for Biological Research (Israel)
Noam Sapiens, Israel Institute for Biological Research (Israel)
E. Fishbine, Israel Institute for Biological Research (Israel)
R. Sahar, Israel Institute for Biological Research (Israel)
I. Egoz, Israel Institute for Biological Research (Israel)
R. Brandeis, Israel Institute for Biological Research (Israel)


Published in SPIE Proceedings Vol. 5319:
Laser Interaction with Tissue and Cells XV
Steven L. Jacques; William P. Roach, Editor(s)

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