The event database contains all event-related information for the World of Photonics Congress.
Lecture Hall ICM - Internationales Congress Center München European Conferences on Biomedical Optics (ECBO) > Translation of Lasers and Biophotonics Technologies and Procedures: Toward the Clinic > Pulsed Laser and Photothermal Applications I
09:15-09:30 h | ICM - Internationales Congress Center München ICM Room 11
Subjects: Biophotonics and Medical Engineering
Chairman: Ralf Brinkmann (, Medizinisches Laserzentrum Lübeck GmbH)
Selective Retina Treatment (SRT) is a laser treatment modality to target the RPE selectively, while causing no thermal damage to the neural retina. The damage mechanism of SRT is based on microbubble formation (MBF). MBF disintegrates the RPE cell before thermal denaturation sets in. In some treatment cases a certain amount of denaturation is required to achieve a therapeutic effect. Thus lasers with variable pulse duration are desirable to handle SRT and photocoagulation. In this context damage thresholds and the differentiation of thermal and thermomechanical damage mechanisms are of high interest. It is the purpose of this work to identify threshold radiant exposure values for different pulse durations. Effects on the neural retina and photoreceptors shall be characterized. A new diode laser source with adjustable pulse duration up to 50 µs is used for irradiation. Porcine RPE serves as model for ex vivo experiments. Chinchilla grey rabbits serve as model for in vivo experiments. Cell damage is identified via calcein vitality assays, fundus photography, Fluorescence Angiography, and Optical coherence tomography (OCT). First ex vivo results have shown threshold values of 394mJ/cm² (5.2µs), 416mJ/cm² (10µs), 562mJ/cm² (20µs) and 753 (50µs). In vivo results have shown threshold values of 675mJ/cm² (5µs), 911mJ/cm² (20µs) and 3507mJ/cm² (50µs) without showing whitening in fundus color images. The study has shown that lesions can be achieved above 1.7µs which are commonly used in SRT with the diode laser system. Although ophthalmoscopically visible lesions have been achieved with 50µs pulses, OCT data have shown significantly lower extend of damage than classical photocoagulation lesions, hardly affecting the photoreceptors.