I am 59 years old and thin. This makes my face seem rather hollowed out, and I also think it makes me look older. Is there an injectable treatment that can fill in these hollowed areas?

Yes. Fillers such as Juvederm or Belotero would work well for smile lines, marionette lines and tear trough areas. If significant volume is needed, Sculptra or Radiesse would work better. It is important to note that surgery will not help with volume loss that occurs with age.