Abstract
Abstract: :
Purpose: To compare the penetration through blood of various laser wavelengths used in thermal photocoagulation, photodynamic therapy (PDT), and transpupillary thermotherapy (TTT). Methods: Laser light (200mW, 0.5 sec duration for visible light wavelengths; 200 mW, 83 second duration for PDT; and 200mW, 30 second duration for TTT) was directed through 2.1 mm normal saline (control), 2.1 mm whole blood with a hematocrit of 40%, and serial dilutions of whole blood. Laser power output was measured with an Orion Laser Power/Energy monitor, Ophir Optronics LTD. Laser power was measured in units of milliwatts and expressed as a percentage of control. Results: Laser power transmission was expressed as a percentage of saline control in all laser wavelength subsets. Conclusion: 521 and 568 wavelengths penetrated the least through all dilutions of blood tested. 689 and 647 wavelengths penetrated most effectively through blood but were still significantly attenuated. This suggests that retinal hemorrhage may have a significant effect on the delivery of laser energy to choroidal neovascular membranes. This may affect parameters used in thermal and non-thermal laser treatments of age-related macular degeneration. CR: none.
Keywords: 454 laser • 308 age-related macular degeneration