Botox: safe injection points for smile lines (lateral canthal lines)

Referred to by their medical name, lateral canthal lines are also known as smile lines, or perhaps more derogatorily as crow’s feet. They are commonly treated with botulinum toxin (Botox®) to reduce their prominence. However, different aesthetic clinicians have different injection approaches, and it is vital to understand the impact that a few millimetres of differentiation with have on the risk to the anatomy and the results you can achieve.

Dr Tim Pearce recently explored the correct Botox injection points for crow’s feet (lateral canthal lines), but in this blog, he discusses some injection points to avoid when treating smile lines with Botox and the anatomy you must consider so you can reduce complication risk and create the best results for your patients.

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Injection point 1: close to the eyebrow

One no-no injection point that Dr Tim has chosen to highlight in his discussion (as you can see from the illustration) is placed quite close to the eyebrow.

Observing its placement on an anatomical model, we can see that it would be affecting the frontalis muscle where the lateral eyebrow is lifted. This is a critical area that we do not want to treat, in most patients, because the lateral eyebrow is so sensitive to dropping, warns Dr Tim.

If we consider the shape of the face, a small drop or change in eyebrow movement laterally will be extremely obvious because it can be easily compared with the other side of the face, meaning there will be an asymmetry, or it can make both sides of the face look tired. It is quite rare that an aesthetic treatment aims to lower a patient’s eyebrows which this injection point would be perfectly designed to achieve, making it a no-no. It will not affect the intended target – the lateral canthal lines – because the placement completely misses the orbicularis oculi muscle.

Injection point 2: tail of the eyebrow

Moving further downwards by a few millimetres, the next injection point to discuss is at the tail of the eyebrow.

This injection point is quite different to the previous one because it is in the bulk of the orbicularis oculi muscle and is correctly placed – assuming superficial injection – to release some of the downward pull from the orbicular oculi where it is pulling on the eyebrow. This provides a subtle way of lifting the eyebrow, with a small botulinum toxin dose, usually, four units of Botox explains Dr Tim.

Placement here should cause the desired effect. However, injecting at the right depth and not going too deep to avoid impacting the lacrimal gland is crucial, he warns.

Injection point three: at the origin of the lateral canthal line

Moving down yet further and still in line with the other discussed injection points is the corner of the smile lines.

This might appear to be a safer and more effective injection point, yet the facial anatomy dictates otherwise because the muscle is arcing away from the eye at this point so the injection would indeed miss the bulk of the orbicularis oculi muscle.

Having a closer look at the anatomical illustration, we see that the bulk of the muscle is lateral to the injection point. This position is medial to the eye, placing the injection potentially very close to another muscle that we do not want to treat – the lateral rectus muscle. If botulinum toxin weakens this muscle, whose job it is to allow the eye to look away from the midline, to look laterally, it will cause double vision when the patient looks in that direction.

Therefore, this injection point is too close to the orbital rim, and we must inject more laterally to keep it safe, advises Dr Tim, another no-no.

This demonstration and blog aimed to highlight some injection points which might appear correct and similar to best practice injection patterns for treating smile lines, but where one would in fact cause a brow drop, one would cause an eyebrow lift, and the other one would cause a lateral rectus palsy if you inject enough dose at a certain depth.

Knowing your anatomy and the impact of your injection points cannot be underestimated in aesthetic medical practice, concludes Dr Tim. Download Dr Tim Pearce’s 26 essential injection patterns for botulinum toxin and read Dr Tim’s other great blog on safe Botox injection points for frown lines (glabella).

Dr Tim is always keen to hear about the experiences of his followers and guide newer practitioners with educational content. So, if you have any questions, case studies, or discussion points for him, you can find Dr Tim Pearce on Instagram.

Aesthetics Mastery Show

Botox Injection points for smile lines

Dr Tim says:

“In this episode I discuss the best injection points to treat smile lines and dive deeper into the anatomy you need to know when treating this area. I also discuss the injection points you need to avoid when treating this area. “

Watch the full Aesthetics Mastery Show here.

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BOTOX (Botulinum Toxin) eLearning Courses

If you want to increase your confidence in botulinum toxin injections, or learn how to avoid and handle complications, Dr Tim Pearce offers two comprehensive courses that are highly rated by our delegates:

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In addition, browse our FREE downloadable resources on complications.

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Dr Tim Pearce MBChB BSc (Hons) MRCGP founded his eLearning concept in 2016 in order to provide readily accessible BOTOX® and dermal filler online courses for fellow Medical Aesthetics practitioners. His objective was to raise standards within the industry – a principle which remains just as relevant today.

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