ABSTRACT
Visualizing retinal photocoagulation by real-time OCT measurements may considerably improve the understanding of thermally induced tissue changes and might enable a better reproducibility of the ocular laser treatment. High speed Doppler OCT with 860 frames per second imaged tissue changes in the fundus of enucleated porcine eyes during laser irradiation. Tissue motion, measured by Doppler OCT with nanometer resolution, was correlated with the temperature increase, which was measured non-invasively by optoacoustics. In enucleated eyes, the increase of the OCT signal near the retinal pigment epithelium (RPE) corresponded well to the macroscopically visible whitening of the tissue. At low irradiance, Doppler OCT revealed additionally a reversible thermal expansion of the retina. At higher irradiance additional movement due to irreversible tissue changes was observed. Measurements of the tissue expansion were also possible in vivo in a rabbit with submicrometer resolution when global tissue motion was compensated. Doppler OCT may be used for spatially resolved measurements of retinal temperature increases and thermally induced tissue changes. It can play an important role in understanding the mechanisms of photocoagulation and, eventually, lead to new strategies for retinal laser treatments.
ABSTRACT
In situ surface imaging for nondestructive evaluation (NDE) by optical coherence tomography (OCT) before, during, and after ablative laser processing is presented. Furthermore, it is shown that the ability of in situ characterization is beneficial for samples such as optical fibers, which are difficult to handle in the standard analysis. Surface images taken by the OCT are compared with these common analysis tools such as scanning electron microscopy (SEM), reflected-light, and confocal microscopy. An axial resolution of approximately 126 nm for surface detection and a lateral resolution <2.5 microm are obtained and the potential of the setup to imaging structures with high aspect ratio is demonstrated.
