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Gereon Huttmann, Heike Müller, Kerstin Schlott, Stefan Koinzer, Lars Ptaszynski, Tim Bonin, Marco Bever, Ralf Brinkmann, Reginald Birngruber; Investigating Of Retinal Photocoagulation By High-speed Oct In Rabbits. Invest. Ophthalmol. Vis. Sci. 2011;52(14):549.
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Photocoagulation of the retina is an important therapeutic option for several retinal diseases. The availability of high-speed optical tomography (OCT) systems now enables the online visualization of thermally induced tissue effects during the coagulation process. Transient changes in intensity and phase of the OCT signal can be observed and e.g. used to calculate tissue expansion and tissue changes with high temporal and spatial resolution With these new options, the tissue effects and the dosimetry of photocoagulation can be investigated in detail.
High-speed optical optical tomography (OCT) with 200.000 A-scans/second was used to study the changes of retinal tissue during and shortly after photocoagulation. Enucleated porcine eyes and eyes of anaesthetized rabbit were irradiated with green laser light at different spot sizes, radiant fluxes, and exposure times. The irradiation was accompanied by optoacoustic measurements of the average temperature increase and continuous OCT imaging of the laser spot and the surrounding tissue.
Morphological changes and also micrometer expansion of the retinal tissue were imaged by using phase-sensitive OCT with good spatial resolution.At low irradiances an expansion of the retinal tissue around the RPE was observed, which was proportional to the temperature development. An additional irreversible tissue expansion was observed at higher irradiance, which was still below the threshold of ophthalmoscopically visible lesions. Visible lesions were associated with an increase of the OCT signal and a distortion of certain retina layers .
In conclusion, high-speed OCT can measure thermal expansion and morphological changes of retinal during photocoagulation in-vivo. It may be used for non-invasive measurements of temperature increases, visualization of tissue coagulation with high spatial resolution, and realtime dosimetry of selective retina treatments.
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