Is there a chance of losing one's sight with upper eyelid surgery.

The risk of vision loss from upper eyelid surgery is extremely rare.  The risk of vision loss related to bleeding into or behind the eye is essentially zero if your surgeon simply removes eyelid skin or a little eyelid muscle.  The risk is slightly increased if the surgeon removes fat from behind your eyelid muscles or if during aggressive muscle excision, the fat compartment is violated and bleeding occurs in the fat compartment without it being controlled.  Aside from bleeding, possible injury to the cornea or eye globe can occur from inadvertent trauma from instruments, etc.  Overall, in the hands of a qualified and experienced surgeon, the risk of vision loss from upper eyelid surgery is so small (well less than 0.001%) that it is an almost complete non-factor when deciding to undergo upper blepharoplasty.  Hope that helps!

Blindness after eyelid surgery

Blindness after a blepharoplasty is extremely rare occurrence. It can be
caused by bleeding that puts pressure on optic nerve. Proper pre-operative
assessment of the patient as well as excellent surgical technique is paramount.
Any patient with unusual pain after a blepharoplasty needs to be assessed on
emergency bases to exclude this type of bleeding.

There is a membrane in the upper eyelid called the septum.  The orbital fat is located just behind this membrane.  If the surgeon wants to take out the fat, this membrane is opened.  It is also opened in a ptosis repair so that you can access the muscle.  Once the septum is opened there is a direct pathway to the back of the eye and the nerve.  If the patient has any bleeding that is not controlled during the surgery, blood may track behind the eye and compress the optic nerve causing visual loss.  Because of this, it is important to make sure there is NO bleeding before you close the incision.  If a patient starts to bleed post-op it is important that they be seen as soon as possible to open the wound which will decrease the pressure behind the eye, and stop any bleeding.  This is a very rare occurrence, but is seen from time to time.