New Anatomy Research on Treating Crow's Feet

A 2022 review by anatomists and clinicians in South Korea proposed a new way of placing neuromodulator injections for crow's feet, based on where the muscle around the eye actually extends and where nearby veins run. It offers a carefully reasoned map rather than tested results, but it highlights why injection patterns should be tailored to each person.

Why this was studied

Crow's feet are the fan of lines at the outer corner of the eyes that deepen when you smile. They form because a ring-shaped muscle called the orbicularis oculi squeezes the skin as it contracts. Wrinkle-relaxing injections of botulinum toxin type A soften these lines by temporarily reducing that muscle's pull. For the basics, see our article on why crow's feet form and how they are treated.

Standard injection patterns use a few points beside the eye. But muscles vary between people, and injecting too close to the eye or too deep can occasionally cause side effects such as double vision, a drooping lid or dry eye. The authors wanted to see whether anatomy research could point to a more precise approach.

What the researchers did

This is a review. The authors gathered earlier dissection, imaging and ultrasound studies on the muscle around the eye and the blood vessels nearby, then used that information to propose a new set of injection points. They did not treat a group of patients or compare their method with standard practice.

What they found

Key anatomical points from the review include:

• The outer edge of the muscle sits, on average, roughly three centimetres from the corner of the eye, though this varies.
• About half of people have an extra band of muscle running from the side of the head toward the cheek, which may influence how crow's feet look.
• The outer part of the muscle is relatively thick and sits close to the surface, so very superficial injection should be enough to reach it.
• A vein on the side of the face commonly passes through the area where crow's feet are usually treated, which matters for bruising.

Based on this, the authors proposed three points set out in a small fan near the outer edge of the muscle, kept back from the bony rim of the eye socket and placed just under the skin. They suggest a smaller dose at the lowest point, to reduce the chance of affecting the muscles that lift the cheek and upper lip when smiling. They also describe using fewer points for people whose lines are concentrated only above, below or beside the eye.

How strong is this evidence?

This is an anatomical review, which is a useful but early stage of evidence. It shows where structures tend to sit and builds a logical rationale for a technique. It cannot tell us whether the proposed method gives better results, fewer side effects or longer-lasting effect, because it has not been tested against current approaches. The authors acknowledge this. Some of the spread estimates they cite also come from animal research, which may not translate directly to human faces.

Anatomical averages are also just that: averages. Your own muscle size, the shape of your lines and how your face moves still have to be assessed in person.

What it means for you

The practical message is reassuring: careful practitioners do not simply use the same pattern for everyone. A good assessment of crow's feet usually involves watching you smile and squint, noting where the lines start and stop, and checking the cheek and lower eyelid. Dose and placement are then adjusted to your pattern. Our article on how neuromodulator dosing is decided explores this further.

Results typically begin within about 3 to 14 days and last around three to four months, though results vary from person to person. Common side effects include small bruises, mild swelling or a brief headache. Less often, the smile may feel slightly different or the lower lid may feel weaker for a few weeks.

Treatment should be avoided during pregnancy and breastfeeding, if there is an infection at the site, or in people with certain neuromuscular conditions. Some medications and supplements can increase bruising, but do not stop any prescribed medication without talking to your doctor.

If crow's feet are mainly etched into the skin even at rest, injections alone may not smooth them fully. In those cases, skin-quality treatments, sun protection and good skincare may play a part, and it is reasonable to ask what combination, if any, makes sense for you.

If your previous treatment wore off quickly or felt uneven, mention it. Our article on when neuromodulator seems to stop working explains some of the reasons.

Questions to ask at your consultation

• How will you decide where to place the injections for my lines?
• Could treatment affect my smile or cheeks?
• What can I do to reduce bruising around the eyes?
• Is a follow-up visit included to check the result?

Frequently asked questions

Will fewer injection points mean a weaker result?

Not necessarily. The aim of a tailored approach is to place the dose where your muscle is most active. The number of points depends on your pattern of lines.

Why do crow's feet injections sometimes bruise?

The skin around the eyes is thin and has many small veins. As this review points out, one vein commonly crosses the treatment area, so bruising can happen even with careful technique.

Can crow's feet injections cause double vision?

It is rare. It can happen if the product affects the small muscles that move the eye. Keeping injections away from the bony rim and using shallow placement is meant to reduce this risk.

If crow's feet bother you, HealthPark Medical Aesthetics can assess your lines and muscle movement at a consultation and explain whether treatment suits you and what a realistic result might look like.

Source

Yi KH, Lee JH, Kim GY, Yoon SW, Oh W, Kim HJ. Novel Anatomical Proposal for Botulinum Neurotoxin Injection Targeting Lateral Canthal Rhytids. Toxins, 2022;14:462. Read the study