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. Optical coherence tomography (OCT) is an emerging biomedical imaging technology which gives high-resolution sectional images of light scattering tissue down to a depth of a few millimeter. The objective of this work is to combine OCT with an operation microscope. A spectral domain OCT was adapted via a specially designed scanning optics to the camera port of an operation microscope. This enables a non-contact on-line OCT during different medical applications. Hidden tissue structures were visualized with a resolution below 30 µm. As a first example for an application in otolaryngology we demonstrated that the OCT operation microscope is basically able to reveal parts of the cochlear morphology without opening its enveloping membranes. Thus it may serve as a helpful guide for the surgeon to exactly localize the scala tympani before opening the fluid-filled inner ear for inserting the electrode array of cochlear implants.

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.

We study the behavior of optical properties of human skin across its layers. We describe ellipsometric measurements for spectrally resolved in vivo investigations of biological tissue. We show in vivo measurements on human skin of the ellipsometric parameters Psi and Delta, which describe the change in polarization of light on reflection on a sample. A tape-stripping study reveals the depth profile of the ellipsometric parameters into the stratum corneum. The depth profile shows an increase in both quantities with increased depth. Analyzing the development of Psi on the number of strips using an exponential function shows a steady state after approximately 2 microm. The evolution of Psi and Delta can be described using a morphological model containing an effective medium approximation accounting for the water content of the skin, surface roughnesses of the corneocytes, as well as the alternating cell and lipid layers.

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