This is bizarre, I have never seen anything like this, but a quick google search gave this

"Having stuck eye caps can cause the eye to eventually dry out and die, then it will basically just "fall" out, but there is usually no blood seen in those cases."
Snake eye falling out? Help! - Redtailboa.net

Although I have no idea how true this is or whether based on fact, the hypothesis of drying out if there is something wrong seems to make sense.