Background: Assessing facial asymmetry is important to prevent unsatisfactory results in rhinoplasty. There has yet to be a consensus on reference lines for determining asymmetry. This study aimed to determine ideal reference lines to assess facial asymmetry and identify predictors of subjective perceptions of facial asymmetry. Methods: Preoperative photographs of 47 patients who underwent rhinoplasty were adjusted according to two reference lines (vertical line from the mid-glabella to Cupid’s bow and horizontal interpupillary line). In total, 94 photographs were generated, randomly ordered, and evaluated by two independent observers for anthropometric measurements including six distances (distances from the midline to the medial and lateral canthi, ala, oral commissure, width of midface at maximum distance, and mandible width) and three angles (lateral canthal, lateral alar, and lip margin angles). Photographs were rated by 18 independent observers for subjective perceptions of facial asymmetry. Results: Observers perceived faces as asymmetric if accompanied by nasal deviation, irrespective of the reference line (p < 0.001). Based on the horizontal reference line, subjective perceptions of asymmetry were correlated with the midline to lateral alar margin distance (r = 0.489, p = 0.003) and sum of the distance ratios (r = 0.354, p = 0.037). None of the objective parameters correlated with subjective perceptions when adopting the vertical reference line. A deviated nose and lateral alar angle were significant predictors of subjective perceptions of facial asymmetry. Conclusion: To assess facial asymmetry, the horizontal reference line should be determined first followed by the perpendicular vertical line. The nose is the most important feature determining overall facial asymmetry. Level of Evidence V: "This journal requires that authors assign a level of evidence to each article. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors www.springer.com/00266.".
- Facial asymmetry
- Reference line