Eye aspect ratio

An eye can look large because it is long, because the lids are open widely, or because it occupies much of the face. Eye aspect ratio describes the opening's height relative to its length. A small rounded eye and a larger rounded eye can therefore share the same result.

Height is measured across the opening perpendicular to the line through the corners. This keeps the opening's shape separate from its tilt. Rotating a long, low eye upwards changes its direction without automatically making its aperture taller.

Opening the lids farther apart raises the ratio when width stays fixed. The additional space may appear mainly above the iris, below it or on both sides, depending on which lid moves. Similar central heights can consequently expose different parts of the eye.

Shorter horizontal openings also raise the ratio without adding height. Flores and colleagues studied 46 white women and found that opening width and height both declined with age, with width declining faster. The eyes became rounder in proportion while becoming smaller overall.

At a low ratio, distinguish a long opening from lids held close together. A long eye can retain ample central height and still have an elongated shape. A temporarily narrowed opening may instead reflect squinting or a partial blink, which is easier to recognise by comparing naturally open photographs.

Relative eye width shows how much of the face the opening occupies horizontally. A high aspect ratio together with long eyes describes a large, open configuration. The same aspect ratio in short eyes describes a rounder shape that may occupy little of the face.

A low aspect ratio with substantial eye width creates a long, low opening. If the outer corner rises, that shape carries an upward diagonal; a level corner keeps it more horizontal. Short openings with a low aspect ratio instead have limited width and height, making the surrounding brow and cheek area more conspicuous.

The inner-eye gap affects how the pair is arranged. Short, round eyes around a wide gap leave more space between the openings than long eyes around the same gap.

A taller opening can expose more of the iris and give an impression of alertness. A lower opening may look relaxed or narrowed, depending on the lids and expression. These are impressions created by the visible boundaries rather than reliable readings of someone's state.

Mogilski and Welling found that eye size affected attractiveness rankings when varied alongside other features. Changing the size of an eye, however, differs from opening its lids or shortening its width. The result gives context for eye prominence without establishing that progressively higher aspect ratios are preferred.

The surrounding face can grow faster than the eye region, making the eyes occupy a smaller share even while their own dimensions increase. Aspect ratio leaves that surrounding scale out of the calculation, so a stable result can accompany a change in how large the eyes look within the face.

In adulthood, opening width and lid position may change independently. Crease visibility and the upper-lid fold also affect the appearance around the aperture. Looking at those features alongside the central opening helps distinguish a change in the eyelids from a change in eye prominence caused by the wider face.

This measurement uses the height at the centre of each eye opening. Measurements taken elsewhere along the lids can give different ratios.

The reference interval is 0.28–0.32. Compare the marked height and width as well: a high result from greater opening height looks different from one caused by short eyes. Inspect each eye separately, since the average can conceal a partial blink or unequal opening heights.