Fig. 2

Locating the FH plane. (a) FS image of the patient in a closed-mouth position. (b) FS image with cheek retractors in place. (c) Superimposition of the FS image in the closed-mouth position over the FS image using cheek retractors, aiding alignment and comparison. (d) The establishment of the FH plane, using the superior margin of the meatus externa on both sides and the right orbitale as anatomical landmarks