In clinical practice, it is not always easy to distinguish the outer choroidal margin on obtained images. The combination of variations in patients, refractive transparency, image quality and anatomy can all affect the determination of the sclerochoroidal interface, which affects the determination of choroidal thickness. A repeatability study of manual SFCT measurements conducted by Rahman et al. observed that a change of more than 32 μm was likely to exceed inter-observer variability in SFCT4. A previous investigation has shown relatively large SFCT measurement agreement in scans with a less visible choroidal outer boundary5. It illustrates the difficulty of locating the borderline of the choroid. To minimize the influence of the linear artifact, the following advice is recommended. First, capture images as clearly as possible. Second, evaluate images under the primary mode, that is, a white line on a black background. Finally, the average depth of the front interface of the linear artifact to the base of the RPE is 485 μm, and the linear artifact is similar to an amplified copy of the ellipsoid zone, the interdigitation zone and the RPE/Bruch’s complex. We hypothesized that this artifact is derived from a mirror mapping of the bands from ellipsoid zone to RPE/Bruch’s complex because the reflexes of the bands from ellipsoid zone to RPE/Bruch’s complex are strong and they are imaged again after secondary reflection by the lens. Caution should be paid to the interpretation of the choroidal thickness, especially when the choroidal thickness is approximately or exceeds 485 μm.