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Diane Nava, Akhila Raman, Claudia Nieuwenhuis, Anwar Nunez-Elizalde, Christine Wildsoet; Spatial and temporal mapping of retinal sublayer and choroidal thicknesses in the chick using 3-dimensional segmentation with optical coherence tomography imaging. Invest. Ophthalmol. Vis. Sci. 2014;55(13):3589.
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© ARVO (1962-2015); The Authors (2016-present)
Interest in changes in thickness of the retina (RT) and choroid (CT) has grown in myopia research, yet studies using animal models typically use A-scan ultrasonography (US), which is limited to on-axis measurements, and blockface photography, which precludes longitudinal tracking. This study sought to exploit in vivo spectral domain optical coherence tomography (SD-OCT) imaging to cover the latter deficiencies.
Young chicks were fitted with either monocular +5 D single vision (SV) lenses or multifocal (MF) lenses with a +5 D peripheral defocus. For each eye, several overlapping rectangular and radial SD-OCT scans covering central and peripheral retina and choroid were collected (14x14 mm FOV, 100 b-scans, Bioptigen, NC). Scans were segmented to extract RT and CT using a custom automated algorithm or a manual segmentation software that uses defined boundaries from points projected from an 11 by 11 grid. The data were then reconstructed in 3D and smoothed using a python-based algorithm. 3D maps of overlapping scans were merged, after which the absolute nasal, temporal, superior and inferior fields were redefined using the angle of the pectin and the location of the area centralis (AC). Interocular and temporal thickness difference maps were obtained through registration. Data were compared to RT and CT from US, photographs of embedded blocks and 10 um vertical sections.
Peripheral choroidal thickening was detected in the MF group. RT and CT data obtained with our custom method were comparable to values obtained from manual calipers, US, blockface photography, and histological sections, with improved inter-observer reliability and resolution. The retinal ganglion cell layer thickness maps show a peak superior and nasal to the tip of the pectin, consistent with histological data defining the AC, and served as a useful reference for validating segmentation algorithms and quantifying lens-induced regional CT changes.
Our new methods for the visualization and quantification of chick SD-OCT data allows for fast and accurate characterization of point-to-point regional and temporal differences in RT and CT in vivo, providing valuable new insight into the effects of novel optical defocus manipulations, as well as ex vivo, providing a replacement for photography applied to blockfaces and histological sections.
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