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M. Yamanari, M. Miura, S. Makita, T. Yatagai, Y. Yasuno; Birefringence Measurement of Retinal Nerve Fiber Layer by Polarization-sensitive Spectral Domain Optical Coherence Tomography and the Comparison With Scanning Laser Polarimetry. Invest. Ophthalmol. Vis. Sci. 2007;48(13):505.
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© ARVO (1962-2015); The Authors (2016-present)
To evaluate the feasibility of polarization-sensitive spectral domain optical coherence tomography (PS-SD-OCT) and to compare the phase retardation of retinal nerve fiber layer (RNFL) measured by PS-SD-OCT and scanning laser polarimetry (GDx-VCC, Carl Zeiss Meditec).
Three dimensional phase retardation and OCT signals were measured simultaneously by PS-SD-OCT whose probe wavelength is 840 nm and the depth resolution is 6.1 um. The polarization-sensitive detection is operated at 27,700 A-scans/second, and the three-dimensional measurement time of the optic nerve head is 5.5 seconds. In order to obtain the retinal Jones matrices, B-scan-oriented polarization modulation method is applied, and a matrix diagonalization method is employed to obtain the phase retardation. Because the corneal birefringence is compensated by the retinal surface, any reference or pre-knowledge of the corneal birefringence is required to obtain correct birefringence of retina. Since the phase retardation obtained by the PS-SD-OCT is cumulative along the depth, the phase retardation at the retinal pigment epithelium (RPE) consists the cumulative effect of the RNFL. The RPE layer is segmented from the intensity image, and the en-face phase retardation map at the RPE layer similar to the phase retardation map of GDx-VCC is obtained. Four normal and two glaucomatous eyes were examined by this method. Some of the en-face phase retardation maps are then compared with GDx-VCC.
In normal eyes, the phase retardation both of the PS-SD-OCT and GDx-VCC around the optic nerve head showed similar double-hump patterns. In glaucomatous eyes, the double-hump patterns both of PS-SD-OCT and GDx-VCC were obscured. A patient, whose superior visual field is severely defected and inferior visual field is moderately defected, showed unbalanced double hump patterns of phase retardation by PS-SD-OCT and GDx-VCC, i.e., the superior phase retardation was evidently less than that of inferior. The intensity images of the PS-SD-OCT showed thinning of RNFL in the severely damaged region.
PS-SD-OCT and GDx-VCC showed similar distribution of the phase retardation. PS-SD-OCT has the potential to diagnose glaucoma using both the phase retardation and the conventional OCT intensity images.
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