The art: mapping, styles and textures

The illusion

A dark fringe makes an eye look larger, by a measured amount

In a Japanese laboratory, 22 people compared one face with and without makeup, step by step. Mascara or false lashes made the eye look about 6 percent larger in width and height. More product did not add more: light mascara on the upper lashes worked as well as mascara with false lashes.¹

Eyeliner alone enlarged the eye step by step, up to about 5 percent, but added nothing once the lashes were darkened. Eye shadow, judged by 104 women across six faces, did about the same. The authors explain all of it as assimilation, the illusion in which a ring makes the circle inside it look larger. That explanation is theirs; the sizes are the measurement.¹

The same lab found that illusions on real faces top out near 5 percent, far below the plain circles of the textbook figure, and suggests faces only tolerate distortions that still look natural. Other labs saw the ceiling from the other side: thicker liner enlarged the eye up to about 1.5 mm, then the effect became erratic and too thick looked wrong.²⁵⁷

Darker lines worked better than lighter ones, and the illusion held when the face was turned or tilted and grew from a distance. On a hooded lid, people chose a thicker line than on a creased lid, 3.4 against 2.6 mm, to get the same effect.⁵⁴²⁶

The eye, measured

The eye a map is drawn on

In 380 adults measured from calibrated photographs, the eye opening was 25.6 mm wide and 8.7 mm tall on average. Measured in 3D, young adults' eyes were about 31 mm wide. The difference is method, not people: the outer corner sits further back than the inner one, so a flat photograph shortens the eye.¹¹¹²¹⁴

Tilt, the height of the outer corner against the inner one, averaged about 2 degrees upward in young adults and about level in older ones. In another group of 300 young adults it averaged 4.7 degrees in men and 7 in women, so normal tilt depends on who is measured.¹²¹⁶

The lid itself varies in structure. A lid without a crease is built differently, with fat in front of the plate of the lid and the lifting muscle reaching the skin nearer the lashes, and the fold over the inner corner has a core of muscle. In 160 adults, lashes pointed further down when the lid had no crease. The upper lid carries 90 to 160 lashes in five or six rows, which is what the trade calls layers.^19202145

The eye's forward position averaged 14.7 mm in a population study of 1,063 people, and inner corners sat 31 to 33 mm apart in the studies above.¹⁸¹¹¹²

Two eyes

Two eyes are never identical, and both change with age

In 69 healthy adults, 87 percent had a measurable difference in height between their two eye openings. Large differences are uncommon: in another study only 5.7 percent had a difference of a millimetre or more. The most uneven feature between two eyes is the height of the lid crease, by an average of 0.65 mm in women and 0.9 mm in men.²⁷²⁶²⁸

Symmetry is attractive across cultures, as are averageness and sex-typical features. Yet upper-eye makeup raised attractiveness without changing measured asymmetry, so its benefit does not come through symmetry.²⁵³²

The eye opening widens by about a tenth between 12 and 25, then narrows by about 2.5 mm between 35 and 85. The eyeball itself does not move; the lids change around it. The outer corner drifts down toward level, the upper lid changes shape from about 40, and lashes get shorter, finer and lighter: 8.0 mm on average in the twenties, 6.4 mm at 50 to 65.^17122223