My mother had a cataract surgery. Everything was fine until the day of follow-up where the doctor told that some tissue had ruptured from some kind of tunnel that was created during the surgery. Due to that there was a brown tissue popping out which was put back after another surgery. According to the doctor,it had happened due to extreme pressure on the eye most probably from squinching of the eye tightly after putting in the eye drops.
PS:- There was no problem in vision and eyesight during the whole time.