Retrograde flow phenomenon of poly-D,L-lactic acid filler injection over lower eyelids.

The occurrence of 'retrograde flow along the cannula/needle tract' during filler injections has not been extensively addressed in the existing literature, possibly because it is often imperceptible unless the injection is conducted at a superficial layer. In our experience with poly-D,L-lactic acid filler for lower eyelid injections, we have observed and documented this phenomenon through the skin. This article aims to elucidate and illustrate the retrograde flow phenomenon and discuss the factors influencing it.