Upper face complications are the subject of a review built around safety zones. A zone is only useful if it is checked before each injection, not recalled afterward.
What the review claims
PubMed Central carries a review of upper face toxin complications. It states: "When the safety zones are respected, the chance of any of these complications is practically null. Thus, this review aims to describe the main complications of treatment with BoNT on the upper face and to present a practical guide based on current evidence on how to avoid them."
The claim is strong, and it depends on one condition. The zones have to be respected every time, including on the tenth patient of the day.
Related reading on complications
For filler complications, which follow their own rules, PubMed Central carries Vascular Complications after Facial Filler Injection: A Literature Review and Meta-analysis. For the condition the toxin is named after, see MedlinePlus on botulism.
A check before each injection
Mark the zones before the needle touches the patient, and treat a deviation as a reason to stop and reassess. Training in Parsippany, New Jersey is no different from anywhere else here: the habit is the protection.
PubMed Central also hosts Complications after cosmetic periocular filler: prevention and management for those who want to read about the area around the eye.