Ultrahigh-resolution imaging of human donor cornea using full-field optical coherence tomography.

A feasibility study of ultrahigh-resolution full-field optical coherence tomography (FF-OCT) for a subcellular-level imaging of human donor corneas is presented. The FF-OCT system employed in this experiment is based on a white light interference microscope, where the sample is illuminated by a thermal light source and a horizontal cross-sectional (en face) image is detected using a charge coupled device (CCD) camera. A conventional four-frame phase-shift detection technique is employed to extract the interferometric image from the CCD output. A 95-nm-broadband full-field illumination yields an axial resolution of 2.0 microm, and the system covers an area of 850 microm x 850 microm with a transverse resolution of 2.4 microm using a 0.3-NA microscope objective and a CCD camera with 512 x 512 pixels. Starting a measurement from the epithelial to the endothelial side, a series of en face images was obtained. From detected en face images, the epithelial cells, Bowman's layer, stromal keratocyte, nerve fiber, Descemet's membrane, and endothelial cell were clearly observed. Keratocyte cytoplasm, its nuclei, and its processes were also separately detected. Two-dimensional interconnectivity of the keratocytes is visualized, and the keratocytes existing between collagen lamellaes are separately extracted by exploiting a high axial resolution ability of FF-OCT.

Analysis of choriocapillaris flow patterns by continuous laser-targeted angiography in monkeys.

PURPOSE: To investigate choriocapillaris flow patterns and its segmental distribution in monkeys by continuous laser-targeted angiography (LTA). METHODS: A slit lamp was modified to incorporate two kinds of lasers (argon and diode). Carboxyfluorescein (CF) was encapsulated in heat-sensitive liposomes and injected intravenously. Encapsulated CF was released locally by applying a continuous heat beam provided by the diode laser (810 nm). Video angiograms were generated with excitation illumination provided by the argon laser (488 and 514 nm), to observe selective images of the choriocapillaris. RESULTS: Continuous application of the diode laser disclosed three distinct phases (filling, plateau, and draining) of fluorescent images of the choriocapillaris. In the plateau phase, a cluster of lobules fed by a common arteriole was uniformly illuminated. This defined area did not change in size while a continuous diode laser was applied to the same spot. Only in posterior regions did the angiograms demonstrate that during the filling and draining phases each lobule was filled from a central spot and drained along a peripheral ring, showing honeycomb flow patterns. In peripheral regions, large choroidal vessels as well as choriocapillaris were observed. CONCLUSIONS: Continuous LTA demonstrated clusters of lobules fed by a common arteriole, and each cluster was found to be functionally independent. There were regional differences in choriocapillaris flow patterns, which suggests that the choriocapillaris provides a more highly efficient system of outflow in posterior regions than in peripheral regions. This modified LTA method appears to be useful in analyzing choroidal circulation in vivo.