In short. The orbicularis oculi both squints and closes the lid. Why its contraction folds the skin radially, and why the same line returns to the same place every time.
Key points
- The lines exist because the muscle that makes them also closes the eye and moves the tear film across it.
- Anything that reduces the fold is working on a muscle with a job to do, which is why the effect is aimed at rather than maximised.
Screwing up your eyes against the sun produces lines that fan out from the outer corner. So does laughing. The pattern is much the same at twenty-five and at sixty, because it is made by a structure every face has in the same place.
A ring of muscle around the eye
The orbicularis oculi is a sheet of muscle encircling the eye socket. It has no attachment to bone at the front: it is anchored at the inner and outer margins of the orbit and lies directly under the skin of the lids and the eye corner. It closes the eye, and the part running around the rim is what narrows it.
Why the folds run outward
Muscle fibres shorten along the direction they run. These run in a ring, so when the ring tightens the circle gets smaller and the skin over it is compressed along the circumference. Skin cannot compress far, so it folds, and because the compression is circumferential the folds stand at right angles to it: radially, pointing away from the eye. That is why the pattern is a fan rather than parallel creases.
A muscle with two jobs
The thin part within the lids closes the eye and sweeps the tear film across its surface with every blink. The thicker part around the rim produces a hard squint, and it also produces the warmth in a genuine smile.
The fan is a signature, not a defect
The lines exist because the muscle that makes them also closes the eye and moves the tear film across it. Anything that reduces the fold is working on a muscle with a job to do, which is why the effect is aimed at rather than maximised.
Why the fold returns to the same place
The dermis is a mesh of collagen and elastin, and once it has been folded along the same line many thousands of times it develops a memory of that line. The fold then forms along that path every time. Creams do not change the direction the muscle pulls.
What the muscle does not explain
The muscle accounts for the crease that appears when you smile. It does not account for a line that stays visible with the face still, or for the fine cross-hatched texture some eye corners develop with age. Those come from the skin itself, which is thinner here than anywhere else on the face.
What this anatomy means in practice
- The fold is made by a muscle, so a treatment aimed only at the skin surface cannot stop it forming.
- The same muscle closes the lid and moves the tear film, so it cannot simply be switched off.
- A line still visible with the face at rest has a component the muscle did not make.
The second component is set out in muscle lines and skin lines at the eye corner. Why this patch of skin behaves differently is covered in why the eye corner ages first.
Frequently asked questions
Why do crow's feet run outward rather than downward?
Because the muscle that makes them is a ring. Muscle fibres shorten along the direction they run, and the fibres of the orbicularis oculi run around the eye. When the ring tightens, the skin over it is compressed along the circumference of the circle, and skin that cannot compress folds instead. Those folds stand at right angles to the compression, which means they point away from the eye.
Does squinting cause crow's feet, or is it only age?
Both are involved and they do different things. Squinting is what makes the fold, and it does so from childhood. Age is what makes the fold persist after the movement stops, because the skin loses the elasticity that used to smooth it out again. A young face has the same muscle contraction and the same transient lines; it simply recovers between movements.
Are the lines deeper on the side a person sleeps on?
Often they are, and many people notice it themselves. Sleeping with the face pressed into a pillow holds the skin at the eye corner folded for hours at a time, which adds to the folding the muscle already does during the day. It is a mechanical load rather than a separate condition, and it is one of the few contributors a person can change without any treatment at all.
Risks & Limitations
- Nothing erases crow's feet. The lines soften with treatment and return as the orbicularis oculi keeps folding the skin.
- Reducing the pull of the muscle at the eye corner can affect lid closure, the tear film and the position of the brow.
- Material placed near the eye corner can show through thin skin, and this is one of the least forgiving areas of the face.
- Resurfacing thin periorbital skin carries a risk of pigment change, redness that persists and, rarely, scarring.
- Treatment in this area is repeated rather than completed, and the decision is remade each time the movement returns.
When to Seek Care
- Difficulty breathing or chest pain — seek emergency care immediately.
- A change in vision, double vision, or pain on moving the eye after treatment to this area.
- An eye that has become dry, gritty or painful, with a lid that no longer closes comfortably.
- Lines that have appeared on one side only, a lid that has begun to droop, or a brow that has fallen.
- A new lump or swelling at the corner of the eye, or a patch of skin that bleeds, crusts or does not heal.
References & Further Reading
- American Society of Plastic Surgeons (ASPS) — procedure and safety guidance
- National Institute for Health and Care Excellence (NICE, UK) — relevant guidance
- Cochrane Library — systematic reviews
- Chinese Medical Association Plastic Surgery Branch — clinical guidance
This page is patient education, not medical advice, and it does not cite individual studies. Discuss your own case with a qualified clinician. To arrange an assessment at Chongqing West District Hospital, see Contact & Consultation.