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M. Pircher, E. Götzinger, B. Baumann, H. Sattmann, C. K. Hitzenberger; Axial Eye Motion Corrected High Speed, High Resolution Simultaneous SLO/OCT Imaging of the Human Retina in vivo. Invest. Ophthalmol. Vis. Sci. 2008;49(13):1892.
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© ARVO (1962-2015); The Authors (2016-present)
To demonstrate the implementation of axial eye motion correction for transversal scanning (TS) optical coherence tomography (OCT), a method that is capable to image the human cone mosaic in vivo.
The instrument is based on a previously reported TS OCT system that can be operated at a frame rate of 40 fps. Additionally, an auxiliary spectral domain OCT interferometer operating at 1300nm is used to measure the position of the corneal apex. This position is used to drive a fast translation stage in the reference arm of the TS-OCT system to correct for axial eye motion. Due to the high transverse resolution of the instrument the depth of field is much smaller than the thickness of the retina. To maintain the high transverse resolution throughout imaging depth, the system is capable to dynamically shift the focus within the retina.
With the proposed method the influence of axial eye motion artifacts was minimized with a residual tracking error of ~10µm. This enabled motion corrected OCT imaging in all three dimensions. The capability of the system to image with cellular resolution could be demonstrated with resolving the human cone mosaic at an eccentricity of ~3-4° nasally to the fovea. The OCT C-scans show an almost identical cone mosaic within two strong backscattering layers anterior to the RPE which we associated with the interface between inner and outer segments of the photoreceptors and photoreceptors end tips. Other details of the retina as inner limiting membrane, nerve fiber bundles, capillaries within the Ganglion cell layer and the inner nuclear layer, could be visualized in high resolution en-face OCT images.
The sensitivity to axial eye motion is one of the drawbacks of TS-OCT systems. With the new method this drawback could be overcome and axial motion corrected TS-OCT imaging can be performed. One advantage of transversal scanning time domain OCT compared to Fourier-Domain OCT is the maintenance of high transverse resolution over the whole imaging depth. Furthermore, the higher transverse imaging speed greatly reduced transverse motion artifacts.
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