Blepharoplasty may involve the removal of skin in some individuals and the removal of fat in others, or the repositioning of fat. It would be best of the physician who would consider doing Utlherapy on you to check with the plastic or oculoplastic surgeon who performed your blepharoplasty. The treatment with Ultherapy usually is not right over the eyelid skin that is treated by surgery as the transduscers, even the small ones, are bulky for this area and the treatment is usually done from the tear trough down on the cheek, not above the tear trough.
There could be some tendency after blepharoplasty for the eyelid to pull away from the eye, especially if too much skin is removed or if the patient has poor elasticity and this pulling away, can occur for months after surgery. It might be that the Ultherapy could exacerbate this by increasing the tightening of the skin.
The information provided in Dr. Shelton's answer is for educational purposes only and is not intended to constitute medical advice. The information provided should not be relied upon as a substitute for consultations with a qualified health professional who may be familiar with your individual medical needs.