Blindness and fillers
Blindness from fillers is extremely rare and very few cases have been reported. If it happens it is usually immediately after injection.
Filler complications under eyes
You are fine. I have done fillers for over 20 years and have never had anyone experience this. When people do, it is nearly always because they went to an inexperienced or unlicensed injector or they received product that wasn't true or real. If you went to a good injector, with good technique, and who uses legitimate product, you don't need to worry about something like blindness.
"This answer has been solicited without seeing this patient and cannot
be held as true medical advice, but only opinion. Seek in-person
treatment with a trained medical professional for appropriate care."