Bipupillary line: the horizontal reference of the face
Quick facts
- Definition
- Imaginary line connecting the centers of the two pupils that serves as the horizontal reference.
- Main use
- Check whether other lines of the face (mouth, eyebrows, jaw) run parallel to it.
- Prerequisite
- Level head, gaze on the horizon, and a photo without tilt.
- Relevance in orofacial harmonization (HOF)
- Prevents mistaking a tilted head for a real facial asymmetry.
The bipupillary line is the imaginary straight line that passes through the centers of the two pupils. In a person with a level head and gaze on the horizon, it is the most reliable horizontal reference of the face, and several other lines are compared against it: eyebrows, the corners of the eyes, the intercommissural line, and the jawline.
Why start with it?
Almost every symmetry analysis depends on an axis. The facial midline marks the vertical axis; the bipupillary line marks the horizontal one. Together they form the cross on which the professional assesses deviations, level differences, and proportions, as in the rule of fifths.
Without this reference, it is easy to treat as a flaw something that is only posture. A slightly tilted head makes the face look asymmetrical even when it is not.
How to check it in a photo and in person
A few precautions make the reading more reliable:
- patient seated or standing, with a level head and gaze straight ahead;
- frontal photo taken at eye level, without tilting the phone;
- drawn lines checked with a level or with the camera grid;
- comparison between the photo and the in-person exam, because lens and angle distort.
What to do when the lines are not parallel?
Divergence between the bipupillary line and the other lines is common and, for the most part, natural. One eye slightly higher, a mouth that rises on one side, or a deviated chin are part of normal facial asymmetry. The decision point is the aesthetic and functional relevance, and the conversation should be honest: not every difference needs to be corrected, and some cannot be corrected with dermal filler alone.
It is also worth remembering the gaze position. The tilt of the eye corner and the Frankfurt plane depend on the same head standardization.
In Harmy
The app's marking is done on a frontal photo. A photo with the head tilted makes the symmetry reading less reliable, which is why the ideal is to photograph level and straight on. The app does not draw the bipupillary line; it is a reference for the professional.
Also called: interpupillary line, horizontal axis of the face.
Frequently asked questions
What is the bipupillary line used for in facial analysis?
It serves as a horizontal ruler: the tilt of the eyebrow, the mouth, and the jawline is compared against it. Divergences suggest asymmetries that deserve a clinical assessment.