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. 2017 Mar 1;6(2):1. doi: 10.1167/tvst.6.2.1

Figure 1.

Figure 1

Thickness measurement error in tilted and stretched OCT image. (A) OCT B-scan image through the fovea as displayed by the Cirrus HD-OCT review software. The image is axially stretched by a factor of 2 compared to its true anatomic aspect ratio. (B) Magnified view of the area outlined in (A). The foveal thickness measured parallel to A-scan (FTx) using the instrument caliper tool was 204 μm and shorter than the thickness of 238 μm as measured perpendicular to RPE (FTy), although on visual inspection, FTx seemed longer than FTy in the displayed image. (C) The same B-scan as (A) converted into an anatomically correct aspect ratio by stretching the image horizontally by a factor of 2. The tilt of the OCT image was milder than (A). (D) Magnified view of the area outlined in (C). Note that FTy (238 μm) was no longer perpendicular to the RPE. FTx was still parallel to the A-scan. FTz is the retinal thickness measured perpendicular to RPE in the anatomically correct image and is considered to be the true thickness value, which is not influenced by image rotation.