What complications can come from a blepharoplasty? How do you handle them?

Generally, upper eyelid Blepharoplasty is a very high satisfaction, low complication type procedure. Lower lid Blepharoplasty has a greater complication rate, but should still be very low in experienced hands.
However, given the question, I will give you the standard run down of complications I explain to may patients (informed consent). Realize that informed consent is a process which allows you to understand exactly what you are proceeding with, not to scare you, but to make sure you are fully educated.
Upper Eyelid:
1) Over resection of skin and inability to close the eyes. I explain to patients that this could happen, but is very easy to avoid. I pinch the eyelid skin while the patient is awake to determine the maximum amount of skin I can safely remove. I then take a little bit less than that.
2) Dry eyes. As we age, we produce less and less tears; every patient gets a temporary dry eye syndrome after eyelid surgery and artificial tears are required. A permanent, clinically significant dry eye syndrome is possible albeit rare and probably more related in nature to over-resection of skin.
3) Asymmetry of eyelid creases. Generally speaking, the lower part of the upper lid incision is made along the upper eyelid crease and correct marking of skin and incision placement avoids this problem. This problem is more likely to occur if the surgeon wishes to reset the upper eyelid crease.
4) Unmasking of pre-existing ptosis. If ptosis (droopy eyelid) is not recognized preoperatively, it generally becomes fairly obvious after the surgery.
5) Bleeding, infection ,scarring. Bleeding is minimal. I have never seen an upper lid incision become infected. Upper eyelid skin is the thinnest in the body and typically forms excellent scars.
Lower eyelid Surgery:
I mention most of the complications above first.
1) Lower lid retraction and/or ectropion. This applies primarily to external approaches, not to transconjunctival approaches. However, in my opinion, an external approach is frequently required to address the tissue descent and skin excess seen with the facial aging process. If excess skin is removed without adequate muscle suspension, the lower lid will lose the battle of the scarring process with the cheek. In severe cases, this can lead to ectropion and corneal exposure. This is an avoidable complication based on experience and judicious technique. It is also more likely to occur in revision cases.
2) Loss of Eyelashes. This is possible but very avoidable via judicious tissue handling and incision placement.
3) Loss of vision. This has been described in the literature via case reports; these reports mainly come from the time period where the anti-platelet activity of aspirin was not recognized, and in cases performed where uncontrolled hypertension was not addressed preoperatively. I have never seen this happen in my community but I always mention it so that a patient is fully informed.

Every medical treatment has risks, and this is true for eyelid surgery as well. Risks of eyelid surgery include bleeding, scarring, dry eye, infection, difficulty closing the eye, corneal abrasion, inadequate (or overzealous) surgical excision of either skin or fat resulting in patient dissatisfaction, eyelid malposition, need for future surgery, anesthesia complications, and more. As long as you choose a well-qualified and well-trained surgeon who can demonstrate experience in the procedures, these risks are generally very low and great results with eyelid surgery are possible.
As with any surgical procedure, if complications do occur, the first step is to notify your surgeon of any concerns and follow their recommendations very closely.
Be sure to see an expert who specializes in facial aesthetic surgical procedures.
All the best,

A blepharoplasty is a wonderful procedure with an amazing outcome and quite low complication. I always perform my signature TBT-eyelift procedure which is a less-invasive and less-traumatic procedure which minimises the risks and complications. Instead of removing the orbital fat which needs a resection/opening of the orbital septum I reposition the orbital fat and leave the septum intact. This septum divides the eyelid from the orbit with its very delicate structures. With the traditional blepharoplasty a major risk is the over-resection of orbital fat which creates a hollow-eye look of the upper eyelid which looks either very operated or even very old (since we loose this fat with ageing). When resecting the orbital fat the lacrimal glands which look similar to the orbital fat could be hurt or removed resulting in a dry eye for life. Bleeding fat might glide back into the orbit after a part was resected and could cause pressure on the optical nerve which can cause blindness. These risks are not involved with the TBT-lift since the septum is not destroyed but only tightened with an external suture. Further complications of an upper eyelift could be a temporary dryness or chemosis (irritation) of the eyes. Risks like conjunctivitis are very rare and more likely occur when an upper and lower eyelift are combined. An assymetric result is very rare but can easily corrected in a minor revision surgery.