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Parallax and asymmetry
Toric soft lenses with makings at 3 and 9 o'clock such as Vistakon's Acuvue Toric have shown that lens decentration can distort the angle of the orientation marks. For instance, in lenses showing inferior decentration, the orientation marks no longer align but appear to slope down in a 'V' shape (Figure 1). This relates to parallax and the fact the lens is tilted slightly when decentered. With an inferiorly decentered lens, the top edge (ie that nearest the limbus) is generally closer to the observer, while the bottom edge sits further away from the observer. As a result, the lens is viewed from an off-axis position and the markings appear to be rotated.
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