Negative canthal tilt

Negative canthal tilt describes an eye whose outer corner sits lower than its inner corner, giving the eye a downward slant. It is the term people most often arrive at this glossary anxious about, so the useful facts first: it is common, it appears across every population, and it is a description of an angle rather than a defect. The usual adult range is around two to eight degrees positive, so a genuinely negative reading is outside that band — but most negative readings taken from selfies are not genuine. A phone held below eye level at arm's length applies enough perspective distortion to flatten or reverse the apparent tilt, which is why a mirror and a photograph so often disagree. Measure at eye level, as far back as your arm allows, before drawing any conclusion at all.