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H. Lee, A. Clemens, C.P. Lin; Monitoring of Intracellular Cavitation During Scanning Laser Targeting of the Retinal Pigment Epithelium . Invest. Ophthalmol. Vis. Sci. 2005;46(13):273.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose:Selective targeting of the Retinal Pigment Epithelium (RPE) using a laser scanner is an attractive method for treatment of retinal disorders that are associated with dysfunctional RPE. Since the selective RPE lesions are not visible ophthamoscopically due to the absence of thermal coagulation, the result of treatment is currently assessed by a post–irradiation fundus angiography. To ensure efficiency of treatment in the clinical setting, a real time feedback system that monitors cell death during irradiation is crucial. The purpose of the current study was to examine the feasibility of cell viability monitoring during the scanning selective RPE targeting by detecting the cavitation–induced back–scattering (reflectivity) change on RPE. Methodology: We have built a laser scanning system employing a continuous–wave (CW) 532nm laser in conjunction with acousto–optic deflectors. The feasibility of real–time monitoring of RPE damage (micro–cavitation) during selective laser treatment was tested using the scanning system with various exposure times (1∼10us). The variation of back–scattered light from the sample was monitored using an avalanche photodiode placed behind a confocal detection pinhole. Intracellular cavitation was detected as a transient increase in back–scattering of the treatment beam. Results:In vitro experiments confirm that we are able to detect cell death during the selective RPE treatment using the scanning system. Currently, 100% of cell death can be detected at 1.3ED50 and 1.6ED50 pulse energy for 1 and 10us exposure time, respectively. Conclusions: We have demonstrated that the backscattering of treatment light can be used to monitor the cell viability during the selective RPE targeting. In the clinic, in order to 1) ensure 100% killing of targeted cells and successful monitoring of the cell viability and 2) minimize potential collateral damage, 1.5 ED50 is expected be a suitable pulse energy setting for treatment. We are optimizing the system to perform in vivo experiments on rabbits by employing the slit–lamp adapted system.
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