5 March 2007 Thermoacoustic wave generation and propagation in the cornea: the potential for damage
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Proceedings Volume 6426, Ophthalmic Technologies XVII; 642628 (2007) https://doi.org/10.1117/12.712253
Event: SPIE BiOS, 2007, San Jose, California, United States
Abstract
Carbon dioxide lasers are used in numerous applications that involve human exposure to the radiation that can produce ocular injury. The objective of this study is to show that the thermal gradient produced in the eye by the radiation from an 80 ns CO2 laser pulse can generate a thermoacoustical tensile pressure wave with large enough magnitude to rupture the epithelial layer of the cornea. A Gaussian-shaped temperature distribution will be employed. It is assumed that the corneal tissue is inhomogeneous, with the density and wave velocity varying slowly in space. Under these conditions, the acoustical wave equation is decoupled into two first-order partial differential equations, one that propagates energy into the eye from the point of thermoacoustical wave generation, and the other toward the front of the eye. These equations are solved numerically using the Lax-Wendroff numerical method. A compressional wave generated in the epithelial tissue of the cornea due to the thermal gradient of the laser arrives at the air-tear layer interface with a pressure amplitude of ~6600 Pa. When this wave is reflected back into the eye, the resulting tensile pressure wave has a tensile strength of approximately 4.6 x 108 Pa/m just inside of the epithelial layer of the cornea. This is an order of magnitude larger than what is necessary to produce cellular damage to the cornea.
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Alvin K. Benson, C. Brent Bargeron, Samuel L. Brady, Adam W. Denning, Leland M. Page, Russell L. McCally, "Thermoacoustic wave generation and propagation in the cornea: the potential for damage", Proc. SPIE 6426, Ophthalmic Technologies XVII, 642628 (5 March 2007); doi: 10.1117/12.712253; https://doi.org/10.1117/12.712253
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