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C. Alt, H. Lee, C. M. Pitsillides, C. P. Lin; Optical Detection of Intracellular Cavitation During Pulsed and Scanning Selective Targeting of the Retinal Pigment Epithelium. Invest. Ophthalmol. Vis. Sci. 2008;49(13):2769.
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Selective targeting of the Retinal Pigment Epithelium (RPE) with a laser scanner can be an attractive method for the treatment of retinal diseases that are caused by dysfunctional RPE. However, exposure success is currently assessed by fundus angiography one hour after irradiation because selective lesions are not visible in slit-lamp examination. Therefore, immediate feedback is lacking and a control system that monitors treatment success during the irradiation is crucial to ensuring a safe and efficient treatment.
Previously, intracellular microcavitation in the RPE was identified as the cell damage mechanism for laser pulses of up to 10 µs during single cell exposure of bovine RPE flatmounts by detecting changes in the backscattered light of the irradiation laser beam.For the current study we have assembled a scanning system that integrates laser, acousto-optic devices, and confocal detector on the slit-lamp and allows simultaneous irradiation of the RPE and monitoring of backscattered laser light in order to detect the formation of intracellular cavitation. The scan pattern was comprised of discretely positioned laser pulses followed by a continuously scanned line, allowing for the direct comparison of pulsed and scanning exposure modalities. Feasibility of monitoring RPE damage during selective laser treatment in vivo was tested in rabbits. The experimental animals in this study were treated in compliance with the ARVO Statement for the Use of Animals in Ophthalmic and Vision Research.
Selective RPE cell damage was accomplished, depending on the irradiation parameters, with accuracy of individual RPE cells. During pulsed irradiation, intracellular cavitation was detected as a transient increase in backscattering signal. Differences in ED50 damage threshold and in detection sensitivity between pulsed and scanning exposures are discussed.
Pulsed and scanning irradiation modalities can be potentially be combined to optimize dosimetry for individual patients in a clinical setting.
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