Figure 1. Threshold Differential Between Perception of Treated Lips and Artificial Lips.

The blue line represents the percentage of observers who thought that the lips appeared treated. The orange line represents the percentage of observers who thought that the lips appeared artificial. dTA₅₀ indicates the threshold differential between perception of treated and artificial lips for 50% of participants, indicated by the grey area between the 2 vertical black lines. dTA₅₀ = 0.9 mm for upper lip only, 1.5 mm for lower lip only, 1.5 mm for upper and lower lips together, 0.6 mm for alteration of Cupid’s bow, and 0.3 mm for extended alteration of Cupid’s bow.