Binned group-average data from the ellipsoid zone (83.5�pth) illustrate estimated attenuation coefficient (eAC) variation according to beam tilt.
<p>The temporal (figure left) and nasal (figure right) retina are analyzed separately. Top: Group mean (±s.e.m.) log-transformed eACs as a function of beam tilt, formatted like in prior work [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0325217#pone.0325217.ref...
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2025
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| Summary: | <p>The temporal (figure left) and nasal (figure right) retina are analyzed separately. Top: Group mean (±s.e.m.) log-transformed eACs as a function of beam tilt, formatted like in prior work [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0325217#pone.0325217.ref009" target="_blank">9</a>]. Black points are used when at least nine eyes contribute to that mean; only those points are used for single-ellipse (blue) and gaussian (red) fits and their accompanying multiple R<sup>2</sup> values, which are calculated with without additional consideration/weighting of the variance at each point. Data from fewer eyes were available at extreme beam tilts (gray points). The peak eAC is at negative beam tilts in the temporal retina, indicating that this part of the retina is most reflective when the OCT beam starts temporal to the optic nerve head, and is aimed nasally (as in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0325217#pone.0325217.g001" target="_blank">Fig 1B</a>). Middle: Data are re-plotted in polar coordinates (“<i>x vs y space</i>”) where tilt and log(eAC) are demarked with the gray radial grid, the model ellipse is centered at (x,y)=(0,0), and the lower half of these plots (where y < 0) describes predictions for |tilt| > 90°. For the nasal retina, the gaussian fit (red) predicts a transparent ellipsoid zone (log(eAC)≈0) for a tilt of ~180° – if the OCT beam first passed through the sclera – in conflict with prior work [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0325217#pone.0325217.ref021" target="_blank">21</a>]. The minimum and maximum eACs (as plotted in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0325217#pone.0325217.g004" target="_blank">Fig 4</a>) respectively are the semi-minor axis and the semi-major axis of a best-fit ellipse. This polar view highlights the orientation of the major reflectors in this part of the retina (dashed blue line; tilted like the orange hash marks in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0325217#pone.0325217.g001" target="_blank">Fig 1C</a>). Bottom: The data are re-plotted in “<i>t vs 1/y</i><sup><i>2</i></sup> <i>space</i>”, where t = x/y, and each point’s x and y values are captured from the middle plots. A quadratic fit in this space (Equation 2) transforms into an ellipse centered at (x,y)=(0,0) in the middle plots.</p> |
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