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Y. Kotera, Y. Yasuno, R. Inoue, S. Makita, H. Nakanishi, M. Yamanari, T. Yatagai, N. Yoshimura, M. Hangai; Fundus Image Obtained by Fourier Domain Optical Coherence Tomography for Glaucomatous Optic Disc. Invest. Ophthalmol. Vis. Sci. 2007;48(13):511.
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To assess the fundus images obtained by three-dimensional Fourier domain optical coherence tomography (FD-OCT) for a glaucomatous optic disc.
Using FD-OCT, 22 eyes of 16 patients with open- angle glaucoma were examined. The OCT system used is a prototype standard-resolution spectral domain OCT system similar to TOPCON 3D-OCT-1000. The acquisition speed is 18,700 axial scans per second. A 3D OCT volume is acquired by a raster scanning using fast horizontal and slow vertical scans. The volume contains 256 (horizontal) × 256 (vertical) A-scans; the acquisition time for this is 3.5 s. In this study, we registered a photograph of the fundus and an OCT projection image by using manually selected control points.
The fundus image obtained using FD-OCT depicted various optic disc structures for which the OCT signal intensity was clearly different. The rim region expressed a low-reflection doughnut shape in the FD-OCT image. For all the eyes, the FD-OCT image showed clearly defined external rim margins. It showed clearly defined internal rim margins in 18 eyes (mean ± SD: 0.14 ± 2.12 diopters) and ill-defined margins in 4 (-1.31 ±2.77 diopters,). A peripapillary atrophy (PPA) in the fundus photograph was depicted as high intensity region by FD-OCT fundus image. Comparison with longitudinal cross-sectional images and color fundus photographs revealed that the external margin of the rim corresponded to the termination of PPA-ß or the retinal pigment epithelium in the area that had no PPA-ß. The internal rim margin was clearly defined when the direction in which the nerve fiber bundle approached the lamina cribrosa was nearly parallel to the probe light.
With the exception of the internal rim margin in myopic eyes, the margins of optic disc structures are clearly displayed in fundus images obtained using FD-OCT based on the differences in the OCT signal intensities of these structures. The imaging method involving FD-OCT images of the fundus is potentially useful to assess the optic disc topography and provide optic disc parameters for the diagnosis of glaucoma.
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