Wait. I assume you are referring to blepharoplasty (cosmetic eyelid surgery.) while there is nothing wrong (theoretically) with combining the two, i favor having the medically-indicated procedure performed first, then the bleph after recovery. Occasionally, there is drooping of the eyelid after cataract surgery (ptosis), this can be corrected at the time of the blepharoplasty.
Separately. Cataract surgery and a blepharoplasty are very different surgeries and have different recovery times. I recommend having one procedure done first and then scheduling the other after you've healed from one procedure. It' may not require months, but just a few weeks.
Wait. Speculum to hold the eyelid open used during cataract surgery can temporarily affect the lid position.
After. Cataract surgery can produce some changes, usually temporary, in lid position. Therefore, i think most surgeons would recommend waiting until you are well-healed from cataract surgery before having lid surgery.
Cataract first. Blepharoplasty (eyelid rejuvenation) can temporarily cause difficulty closing the lids completely. The resulting dry eyes is not a big problem usually, but would not be good immediately after cataract surgery. That is my point of view after discussion w/ local eye md's. Be sure to discuss with your ophthalmologist in detail.
After. I would not recommend having both at the same time for two reasons. First, there have been reports of increased complications and second, the swelling from the eyelids can put pressure on the eye and affect the wound. So, i would do the cataract first and the lids after the cataract is healed.
Not at same time. I would not recomend at the same time. I would wait at least 90 days after lid surgery to have cataract surgery. Or wait 30 days after cataract surgery to have lid surgery.