Ideal Reference Lines for Assessment of Facial Asymmetry in Rhinoplasty Patients

Lee KH, Kang JW, Lee HY, Kim SJ.

PubMed 34498143 Publisher (DOI)Free full text (PMC)

What this paper says

Testing two reference lines on photographs of 47 rhinoplasty patients rated by 18 observers, faces were perceived as asymmetric whenever the nose was deviated, regardless of which line was used.

Overview

Assessing facial asymmetry before rhinoplasty matters for avoiding unsatisfactory results, but there is no agreement on which reference lines to use. The study aimed to identify the best reference lines and to find what predicts whether observers perceive a face as asymmetric.

Sections of note

Preoperative photographs of 47 rhinoplasty patients; the journal assigns level of evidence V.
Two reference lines were used: a vertical line from the mid glabella to Cupid's bow, and a horizontal line between the pupils.
Ninety four photographs were generated, randomly ordered, and measured by two independent observers.
Measurements were six distances and three angles, including midline to eye corner, nostril wing, mouth corner, midface width and jaw width.
Eighteen further independent observers rated each photograph for perceived asymmetry.
Faces were perceived as asymmetric whenever the nose was deviated, regardless of reference line, P less than 0.001.
With the horizontal line, perceived asymmetry correlated with the midline to lateral alar margin distance, r equals 0.489, and with the sum of distance ratios, r equals 0.354.
With the vertical reference line, no objective parameter correlated with perceived asymmetry.
A deviated nose and the lateral alar angle were significant predictors of perceived asymmetry.

What it means for a patient

Observers judge a face asymmetric largely because of the nose, not the rest of the face.
The authors conclude the horizontal line between the pupils should be set first, then the vertical line drawn perpendicular to it.
Ratings came from independent observers viewing photographs, not from the patients themselves.
Forty seven patients from one centre, assessed only before surgery, is limited evidence.

Why this paper matters

Facial asymmetry affects satisfaction after rhinoplasty but has been measured inconsistently because reference lines differ between studies. This study tests which lines correspond to how people actually perceive asymmetry. Whether using them changes surgical planning or outcomes is unaddressed.

Terms

Reference line: a line drawn on a photograph to align and measure the face.
Glabella: the flat area between the eyebrows.
Interpupillary line: a horizontal line drawn between the centres of the pupils.
Lateral alar margin: the outer edge of the nostril wing.
Nasal deviation: the nose bending to one side rather than running straight.
Correlation coefficient r: a measure of how strongly two variables move together.

Summary written by rhinoplasty.cc from the abstract, 2026-09-09; not medical advice. The authors' own abstract follows.

Abstract

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 ."

Abstract as indexed by PubMed; the article is open access (PubMed Central).