Had filler under eyes over a year ago. My right eye became swollen over the last 6 months, what could have caused this? (photo)

Post-filler swelling like this can occur as a result of lymphatic drainage obstruction due to improper choice of filler and/or too superficial placement of the filler in the delicate under eye tissue. The problem is very typically difficult to treat, but I have had success with using a combination of hylauronidase and intralesional anti-inflammatory agents in varying combinations and concentrations. Typically a series of treatment sessions are required. Make sure to consult with an experienced, board certified cosmetic dermatologist. Hope this helps. Best of luck.

Delayed swelling or edema even months after the placement of undereye filler is not uncommon. The undereyes and tear troughs are very sensitive areas. Even when the filler is done well, complications are fairly common. Many physicians and surgeons more commonly recommend surgery or laser resurfacing as safer and more effective alternative treatment for these areas. However, in the right patient, undereye filler can be appropriate.
In your case, you could try a short course of oral steroids such as a Medrol Dose Pack to see if it helps with the swelling. After that, dissolving the filler with hyaluronidase is most likely going to be your best option. Fortunately, this is not likely going to be associated with any long-term negative side effects. Once the filler is dissolved, you may consider one of the other options I noted above.
I hope this information is helpful.

Without an exam, it is hard to tell. The picture seems to be a relatively straightforward tear trough. However, if the Volite was injected deep, it could have caused lymphatic blockage resulting in the problem that is different from the other side. Volite is not a “filler” designed to be placed deep, it is supposed to be placed in the bottom of the dermis to stimulate collagen production. I suggest you see an expert injector who thoroughly understands the area.