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Young Jung Roh, Eric Seifert, Theisen-Kunde Dirk, Young Gun Park, Seungbum Kang, Ralf Brinkmann; Selective retina treatment (SRT) automatically controlled by a real-time reflectometry in a rabbit model. Invest. Ophthalmol. Vis. Sci. 2013;54(15):4136.
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Selective retina therapy (SRT) targets the retinal pigment epithelium (RPE) with repetitive microsecond laser pulses, while causing no thermal damage to the adjacent photoreceptors. Our purpose was to evaluate the safety, selectivity and healing of the retinal lesions by using an automatic dosimetry technique for SRT basing on the evaluation of reflected light during irradiation.
Ten eyes of Chinchilla Bastard rabbits were treated with SRT (wavelength: 527 nm, pulse duration: 1.7 µs, repetition rate: 100Hz, max. number of pulses in a burst : 30, pulse energy : 88 µJ, retinal spot diameter : 200 µm) using a Q-switched Nd-YLF laser controlled by real-time reflectometric dosimetry. The technique ramps up the pulse energy within in a burst until microbubble formation is detected and then ceases laser irradiation. After treatment, fundus photography, optical coherence tomography (OCT) and fluorescein angiography (FA) were performed at 3 time points from 1 hour to 3 weeks. Histological analysis was done after 3 weeks.
Typical fundus photographs obtained 1 hour after irradiation showed that all lesions produced by SRT were not visible ophthalmoscopically at all energy levels used. The lesions could be detected only by angiography. No sign of disruptive effects, such as hemorrhage, was observed. Fundus examination showed focal pigmented speckle due to healing status and no fluorescein leakage after 7 days. OCT images revealed the structure of photoreceptor was preserved, but a disrupted RPE layer as expected. By 3 weeks, histology showed selective RPE damage sparing photoreceptor continuity without inner retinal effects and focally proliferated.
SRT achieves selective targeting of the RPE without permanent scarring or inner retinal damage. Reflectometry is a reliable noncontact technique to monitor RPE disintegration and may serve as real-time dosimetry control during SRT.
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