Selective damage of pigmented cells by means of a rapidly scanned cw laser beam

摘要

Selective targeting the retinal pigment epithelium (RPE) while sparing adjacent tissue such as the photoreceptors has been demonstrated by repetitively irradiating the fundus with a train of green μs-laser pulses. The aim of this study was to investigate selective RPE effects alternatively by means of rapidly scanning a cw-laser beam across the RPE to obtain the required μs-illumination times. The radiation of an Ar~+ laser (514 nm) was transmitted through a 25 μm core diameter fiber to a scanner unit. The fiber tip was imaged onto the object plane with a magnification of 0.75. The beam was repetitively scanned across porcine RPE samples in vitro providing an irradiation time of 1.6 μs. Cell damage was investigated with a fluorescence viability assay. The ED_(50) cell damage power was determined to 580 mW when applying 10 exposures with a repetition rate of 500 Hz. It decreases to 250 mW for 500 exposures and more. The threshold keeps constant for an axial focus displacement of about 250 μm. In conclusion, selective cell targeting has been proved with a laser scanning device. The technique can be adapted for clinical RPE treatment to a slit-lamp or by modifying a retina angiograph.