Conscious Perception of Facial Asymmetry in a Unilateral Cleft Lip Model.

OBJECTIVE: Lip asymmetry after a unilateral cleft lip repair can be perceived as an unsatisfactory result. The objective of this study is to determine the degree of upper lip asymmetry and/or nasal alar hooding required for recognition of asymmetry in a simulated model of unilateral cleft lip. DESIGN: A model of unilateral cleft lip was created using digital morphing software to simulate asymmetries in vermilion height and nasal hooding in photographs of children. Volunteers were shown photographs for different time intervals and with varying degrees of asymmetry. Ability to detect facial asymmetry was recorded and analyzed. SETTING: This study was conducted by surveying layperson volunteers in public community settings. PARTICIPANTS: 108 layperson volunteers were randomly surveyed. MAIN OUTCOME MEASURES: The primary outcome measure was a reported lip or nose asymmetry by the volunteers. Proportions and corresponding 95% confidence intervals were obtained to estimate the probability of reporting an asymmetry at 3- and 10-second intervals. RESULTS: After 3- and 10-second exposure, labial asymmetry was perceived by ≥50% of subjects at 2 mm (62%, P = .001) and 1 mm (89%, P < .0001), respectively. Nasal asymmetry was detected by <50% of subjects at 3 seconds, but ≥50% perceived a 3-mm alteration at 10 seconds (64%, P < .0001). Photographs with combined nasal and labial modification did not lower the threshold for asymmetry perception compared to either deformity alone. CONCLUSIONS: This study is the first to determine a predictable millimeter threshold for perceived asymmetry in cleft lip deformity using a digital model.