A simple computerised technique for estimating resting lip position and symmetry.

Area of Science:

• Medical imaging
• Facial analysis
• Biometrics

Background:

• Assessing facial symmetry, particularly lip position, is crucial in various clinical applications.
• Existing methods for quantifying lip symmetry may lack precision or repeatability.
• The commisure-commisure to endocantus-commisure (CCE) angle offers a potential metric for lip symmetry analysis.

Purpose of the Study:

• To establish the repeatability of a computerized technique for measuring the CCE angle.
• To determine mean CCE angle magnitudes in a healthy control group.
• To define a "normal" reference range for CCE angle asymmetry.

Main Methods:

• Two independent authors measured CCE angles on facial photographs of 104 volunteers across three sessions using specialized software.
• Symmetrical facial images were created by mirroring hemifaces with the largest CCE differences.
• Inter-rater and intra-rater reliability were assessed using intraclass correlation coefficients (ICCs).

Main Results:

• High inter-rater (ICC=0.89) and intra-rater (ICCs=0.85, 0.77) agreement was observed for CCE angle measurements.
• Statistically significant, though small, differences were found between mean right (82.4°) and left (81.7°) CCE angles in controls (mean difference 2.2°).
• A "normal" reference range for CCE angle asymmetry was established as 0.2°-6.2° (95% interval).

Conclusions:

• Computerized CCE angle measurement demonstrates high repeatability and reliability.
• The developed technique is a potentially valuable tool for assessing gross resting lip symmetry.
• A defined normal reference range aids in the interpretation of CCE angle asymmetries.