PRP is probably the safest injection for the under eye area. There is risk of bruising and swelling but you don't have to worry about lumpiness or discoloration. PRP is not going to give you volume like a filler because it works by releasing growth factors that help to regenerate tissue in the area. The results are going to be very subtle and you will need multiple sessions. Combining PRP with micro needling or radio frequency treatments will further help enhance results. If you have significant volume loss, you might want to consider a fat grafting procedure, which will give you a very natural and long lasting result if performed by a skilled physician.