Abstract
Abstract: :
Objective:To quantify the in vitro energy attenuation by blood of the laser used in verteporfin photodynamic therapy. Methods:The spot size of a 689 nm laser used in photodynamic therapy was adjusted until a power sensor showed the output through air was 100 + 0.55 milliwatts (mW) (mean + standard deviation). Cuvettes 10, 50, 100, 200, and 500 microns thick were placed in the path of laser light from the slit lamp to the power sensor to approximate the location of an eye being treated. A purple top blood collection tube containing ETDA was filled with balanced salt solution (BSS). The ETDA/BSS mixture was placed in each cuvette, and absorption of laser light measured. A second purple top tube was filled with blood from the senior author (hematocrit 46.7%). The anticoagulated blood was then substituted for the EDTA/BSS mixture in each cuvette, and the absorption of laser light again measured. All measurements were based on the mean of six readings. Results:The power sensor readings for the 10, 50, 100, 200, and 500 microns thick ETDA/BSS filled cuvettes were 93.58+0.82, 94.67+1.47, 94.20+0.64, 95.30+0.36, 94.88+0.71 mW, respectively (mean + standard deviation). The power sensor readings for the same cuvettes filled with ETDA anticoagulated blood were 45.02+1.39, 28.25+1.48, 11.00+0.67, 5.77+0.32, and 1.29+0.06 mW. The transmission of laser energy through blood as a percent of the transmission through the EDTA/BSS filled cuvette was:
Conclusion:Even small amounts of blood significantly reduce the transmission of the 689 nm wavelength laser used in verteprofin photodyanamic therapy.
Keywords: photodynamic therapy