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A. Nagata, T. Higashide, S. Ohkubo, H. Takeda, T. Nakagawa, K. Yashima, M. Hasegawa, K. Sugiyama; In vivo Quantitative Evaluation of Rat Retinal Nerve Fiber Layer Using Optical Coherence Tomography. Invest. Ophthalmol. Vis. Sci. 2008;49(13):5471.
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© ARVO (1962-2015); The Authors (2016-present)
To determine whether optical coherence tomography (OCT) is useful for quantitative evaluation of rat retinal nerve fiber layer (RNFL) thickness using an optic nerve crush model.
An experimental OCT system was developed with a commercially available OCT (EG SCANNER; Microtomography Corp., Japan) and a multiplexed two-superluminescent-diode light source (Broadlighter; Superlum Diodes, Ltd., Moscow, Russia) with a center wavelength of 890 nm, a bandwidth of 150 nm, a coherence length of 4.5 µm, an axial imaging resolution of 2.2 µm, and an output power of 6 mW. Optical components in the experimental OCT system were optimized to acquire retinal images of rats. Male Brown Norway rats, 8 weeks of age, were used in this study. After rats were anesthetized by an intraperitoneal injection of sodium pentobarbital, the optic nerve of the right eye was crushed intraorbitally with a clip. The left eye served as the untreated control. Cross-sectional OCT imaging was performed in a circumpapillary fashion, with a circle diameter of 500 µm centered on the optic disc before and 1, 2, and 4 weeks after optic nerve crush (12 eyes of 6 rats). Four weeks after optic nerve crush, cross-sectional OCT imaging was additionally performed in a linear fashion at 400, 500 and 600 µm apart from the center of the optic disc. Thereafter the eyes were perfusion fixed with 4% paraformaldehyde/ 0.5% glutaraldehyde in a phosphate buffer, embedded in paraffin, and sectioned. The RNFL thickness in retinal sections at the corresponding locations to linear OCT scans was measured and compared to that in OCT images taken before histologic preparation (6 eyes of 3 rats).
RNFL thickness before and 1, 2, and 4 weeks after the optic nerve crush was 28.8 ± 1.0, 30.4 ± 1.8, 20.9 ± 0.8, 4.6 ± 4.2 (the mean ± SD), respectively. The RNFL thickness was stable 1 week after optic nerve crush, but then decreased significantly and progressively after the second week (P < 0.001). The RNFL thickness in OCT images was correlated significantly with that determined histologically (r = 0.92, P < 0.001).
OCT is a useful and valuable tool for quantitative evaluation of rat RNFL thickness.
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