Sudden sagging of skin, loss of fat in cheeks and sunken eyes one year after rhinoplasty, what could the cause be?

It is unlikely that a sudden change in facial soft tissue appearance would be related to a rhinoplasty performed one year prior. While changing one facial structure can definitely affect the overall facial harmony and the perceived appearance of surrounding structures, this is not something that would become evident one year later. 
Other factors that might affect the soft tissues would include aging, sun exposure, stress, fatigue, or infection. Be sure to get a formal evaluation by a facial plastic surgeon or plastic surgeon specializing in facial aesthetics in order to determine the best treatment options.
All the best,

Hello,Thanks for your question. I agree that this sudden change in your face is not due to your rhinoplasty. Often this type of change occurs with weightloss or illness. I would discuss your concerns with your surgeon, compare preop photos to your one year postop photos, and also get a check up at your doctor's office.Good luck,Dr. Shah

The facial changes that you are describing are totally unrelated to your rhinoplasty. Given your description of the changes, it would be extremely wise to  see your primary care doctor for a full evaluation as something significant is going on that needs to be evaluated (and you didn't describe a substantial and intentional weight loss).Steven Turkeltaub, MD

Sudden changes in weight and face are reasons to be concerned about. You need to get yourself checked medically. These are not related to your rhinoplasty. After complete check up you might consider correction of these facial changes with other facial plastic surgeries and procedures.