Fluid Drain for scleral buckle surgery

My doctor said during the scleral buckle surgery he may have to drain fluid by sticking a needle in my eye.  He said the risk, obviously, is bleeding in the eye.  He won't know if he has to do this until he's doing the surgery.  What is this called and what are the odds of bleeding?  What would be done to stop it and can it be reversed?
Thank you in advance.

[Forum-OD-MP]

paracentesis:

http://bjo.bmjjournals.com/cgi/content/full/88/4/582

dont know the "odds" of bleeding.  but they're probably low IMO.  dont know what could be done to stop it...