I received Restylane Silk injections under my eyes a year ago. Today my filler is swollen and tender. What is going on?

Restylane should dissolve over the course of about a year. If you were having any kind of reaction to the filler it likely would have been at the begging or shortly after your treatment. I would recommend seeing a doctor and getting the remainder of the filler dissolved.

Thanks for your question and helpful photos.  It's a little hard to tell if there is a problem with the filler, or if something else is going on, but sometimes people do develop late complications or nodules after even the softest fillers.  The tear troughs are notoriously tricky to inject.  I would recommend returning to your injector and seeing if they think this is a granuloma or nodule from filler, and ask if they think dissolving it with hyaluronidase would be helpful.  Sometimes that helps, but it is also something only an advanced, experienced injector would be best at doing.  Please see an expert, and best of luck!