Within any purely Asian or purely Occidental population, there exists a great deal of natural eyelid, orbital, and facial anatomic variation. In a patient of shared Asian and Occidental inheritance, there is, quite simply, a larger range of possible variation.

In general, patients of mixed lineage possess less upper eyelid fat and at least some evidence of a preexisting upper eyelid crease. As demonstrated below, development of the epicanthal fold is highly variable.
Since blepharoplasty -- Asian or Occidental -- is not a stock operation, all surgery is planned to take into account each patient's anatomical features, any imposed limitations, and individual desires regarding outcome.
As long as such factors are identified and respected, the blending of Asian and Occidental traits presents little added challenge in double eyelid surgery.