Because most eyelid anatomy is affected by the position of the brow, it's best to allow the Botox effects to diminish. This, in most cases, takes three months.
Botox as well as the other neurotoxins that are available to us in the United States currently typically last 3-4 months. I therefore recommend that you wait 3-4 months prior to your blepharoplasty. It is ideal for there to be no muscular relaxation when planning for the blepharoplasty. Best of luck to you. I hope this was helpful.