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A. F. Walter, P. Prahs, J. Hillenkamp, R. Brinkmann, V.-P. Gabel, C. Framme; First Clinical Evaluation of Selective RPE Laser Treatment (SRT) With 200ns Laser Pulses. Invest. Ophthalmol. Vis. Sci. 2007;48(13):5095.
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© ARVO (1962-2015); The Authors (2016-present)
Selective RPE laser treatment (SRT) solely affecting the RPE while sparing of the photoreceptors is usually performed with repetitive laser pulses of 1.7µs duration. It was our purpose to evaluate firstly the principle feasibility of using shorter 200ns laser pulses in patients treatment and to determine the angiographic and ophthalmoscopic damage thresholds.
Patients with macular disorders [diabetic maculopathy (DMP), geographic atrophy (GA), drusen maculopathy and central serous chorioretinopathy (CSR)] were treated with a prototype of a SRT laser (Med. Laser Center Luebeck GmbH, Germany: Nd:YLF laser; 527nm; 200ns pulse duration; 30 pulses at 100Hz). In average, 16 to 20 spots with a diameter of 200µm were applied. Test lesions with increasing energy were applied at the lower arcade to determine the angiographic and ophthalmoscopic threshold radiant exposures and then to apply the treatment lesions with radiant exposures in between the therapeutic window of both thresholds guided by online optoacoustic measurements. Postoperatively RPE damage was visualized and confirmed by fluorescein angiographic leakage.
None of the short repetitive 200ns laser pulses led to retinal hemorrhages or retinal ruptures. All treatment lesions were ophthalmoscopically invisible suggesting intact neurosensory retinal structures. RPE damage could be confirmed by angiographic leakage for the treatment lesions. The angiographic damage threshold was determined to be about 100µJ, the ophthalmoscopic one at least about 200µJ. Thus, damage thresholds were significantly lower at a factor of about 2 instead of treating with 1.7µs (angiographic threshold: about 200µJ) using the same laser prototype for same diseases.
Selective RPE effects can be achieved using shorter 200ns laser pulses in patients treatment. Applied threshold radiant exposures to reach RPE damage were significantly lower than for 1.7µs laser pulses indicating a reduced heat flow into adjacent tissues during the short laser impact.
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