Blepharoplasty surgery left a ridge under left eye - it's 2 months post surgery. (photo)

Its still early to fully judge the results, but its possible its just a small amount of edema or swelling under the incision, or some muscle hypertrophy.  it might be small amount of bunched skin that hasn't settled down yet. I would wait a full 6 months. In the mean time, a small amount of kenalog (dilute) might be helpful in having that skin flatten out. Good Luck!

You are still early in your recovery stage.  If the ridge is still noticeable in another 2-3 months, consider  treatment with Botox to see if it is an orbicularis ridge.  If it persists, then consider some judicious use of dilute Kenalog. 

I think it is hard to say what is causing this but it will definitely improve over the next couple of months without any treatment.  Fluid and scar tissue persist for at least 3 months following the surgery and then start to improve over the next 6 to 12 months.  While it's hard to be patient, the body's ability to heal is amazing. Hang in there and I wish you the best of luck.