Hollowness after lower blepharoplasty. Is this normal?

Usually transconjunctival lower blepharoplasty with repositioning of the fat bags is a very effective procedure but the result does depend on the amount of fat bags present, the technique used, and healing process.

The goal of the arcus marginalis surgery is to preserve the fat that makes a bulge in the lower eyelid and move it to the top of the cheek to provide volume as a living pedicle graft. When it works, it is wonderful. In some cases, the doctor over promises the effect of surgery and under delivers. It happens. In some cases, the surgery found very little orbital fat, removed skin and resuspended the lower eyelid. That leaves the tear trough relatively under filled.  In that case, the fillers can be very helpful. And yes, under those circumstances, you may have been better off simply having filler.  Generally I will recommend filler if I think it will successfully handle the lower eyelid and reserve surgery for those situations that can't be managed with filler.

It would be unusual to have significant hollowing after a lower lid fat repositioning unless you had very little fat to begin with.  In some patients we try to save and move whatever fat there is, but it still may not be enough to fill the tear trough.  In those cases some filler is helpful post-op.