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Stefan Zotter, Michael Pircher, Teresa Torzicky, Bernhard Baumann, Philipp Roberts, Ivania Pereira, Stephan Holzer, Clemens Vass, Ursula Schmidt-Erfurth, Christoph Hitzenberger; Evaluation of retinal nerve fiber layer retardation, thickness and birefringence along the major nerve fiber bundles measured with polarization sensitive OCT. Invest. Ophthalmol. Vis. Sci. 2013;54(15):4803.
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© ARVO (1962-2015); The Authors (2016-present)
To evaluate the retinal nerve fiber layer (RNFL) retardation, thickness and birefringence along the major nerve fiber bundles within healthy human subject using polarization sensitive OCT (PS-OCT).
For this study a recently presented PS-OCT system was used. The instrument provides a maximum scan field of 40° x 40° and operates at an A-scan rate of 70kHz. Currently 10 eyes of 5 healthy subjects are included in the study. 3D measurements of the optic disc area were performed and RNFL retardation, thickness and birefringence maps were generated for each dataset. For quantitative analysis seven evaluation boxes were placed manually along the large nerve fiber bundles superior and inferior to the optic disc. The mean retardation, thickness and birefringence was calculated within these boxes and plotted against the distance from the center of the optic disc. The resulting curves were averaged for all eyes included in the study.
The mean RNFL retardation within our study group started at a value of 37.2° superior at 5° eccentricity from the center of the optic disc (37° inferior) and decreased to 24.2° at 12° eccentricity (23.6° inferior). The mean RNFL thickness superior at 5° eccentricity was measured to be 163.6µm (175.7µm inferior) and decreased to 127.9µm (123.2µm inferior) at 12° eccentricity. The mean birefringence exhibited a value of 0.147°/µm superior to the optic disc at 5° eccentricity (0.14°/µm) and remained widely constant along the major nerve fiber bundle. The mean birefringence at 12° eccentricity was 0.138°/µm superior and 0.141°/µm inferior.
The mean RNFL retardation, thickness and birefringence were evaluated along the large nerve fiber bundles within the human retina. We found that the retardation and thickness decreases with eccentricity from the optic disc whereas the birefringence remains widely constant. Further measurements on a larger study population are planned to support these findings.
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