There is no item that triggers the door. You have to find the picklocks and go into Dr. Brundle's office.
Ok, I picked up the eyeless body, the "fog" and monster showed up, played the third tape and saved, then it went back to normal, the door is shut, and the only thing to interact with are the notes and doors, as well as the two blind monsters in that one room.
I'm pretty sure when you get into Dr.Brundles office and pick up the eyeless corpse, the red eye'd monster show up. It gets darker and foggy, and the door with the retina scan should open on it's own. At this point I hadn't played the tape or saved so instead of going to the door I went back, and after I went back into the Lab it was no longer darker. The monsters were gone, the office was already picked open, I have the body, and the door is shut.
Also I doubt it would matter but it was past 12 when I was playing, and when I tried restarting I played midnight mode instead.
To sum it up I have the body, but the door is shut.
?????????????? Sounds like some serious sequence breaking. I'll look into it and try to figure out what happened. Normally it should be, find the doll head, break it and retrieve the picklock, get into the office, the body doesn't matter, the door should be open. I'm guessing you somehow got the area to progress further than it should have and that's why the retina door is locked. There must be a trigger somewhere that doesn't get deactivated properly so it's firing twice. If you want to fix it manually you can use regedit.msc, go to HKEY_CURRENT_USER, Software, Lag Studios, Lost in Vivo, and change SAVED_LAB_02G to 3. And then start the game. If it is higher than 3 please let me know.