Is half a syringe of Restylane enough to get noticeable results under the eyes?

yes that could be ideal...but without examining you it would be impossible to ascertain.  N.B. it injrctor and experience of injector in this area is paramount

Thank you for sharing your question. Typically, half syringe is enough, but it is not possible to determine what you require without evaluation. See an experienced eyelid specialist for your treatment in this delicate area. Good luck,