The director at our clinic about 12 years ago when he just returned to Japan he had a lecture for a Japanese doctor.
At that time he already mentioned that it may lead to blindness rarely as a US report with hyaluronic acid or other subcutaneous infusions. In particular, special care is required for injection into the areas near eyes, between the eyebrows and the nose root. It is better not to inject such sites as much as possible, and when it is absolutely necessary to avoid excessive injection depth and speed (pressure).
The filler injection might appear an easy procedure but because of rare yet serious complication that my occur, a board-certified plastic surgeon or dermatologist should be doing the procedures.