Hayden Christensen had to look through the mouth-piece of the Darth Vader costume, not the eyes. See more...
Popular blog posts:
Other great sites
Star Wars: Episode III - Revenge of the Sith (2005) - 156 continuity errors
Directed by George Lucas, starring Ewan McGregor, Hayden Christensen, Ian McDiarmid, Jimmy Smits, Natalie Portman, Samuel L. Jackson, Anthony Daniels, Christopher Lee, Frank Oz, James Earl Jones, Kenny Baker, Peter Mayhew (add more)
In the scene where Anakin arrives on Mustafar and tells R2-D2 to stay with the ship, he pulls the hood of his robe over his head with two organic hands. His right hand should be mechanical. [This mistake is mentioned in the audio commentary: this shot is taken from a shot of Obi-Wan later in the film when leaving Padme's apartment. Still a mistake, though.]
When Anakin is in the medical centre lying on his back being transformed into Darth Vader, you can see the main part of the mask being lowered into place but Anakin is not wearing the neck section of the mask that it connects to. We then see the main part lowering directly downwards, in the next shot the neck section is in place.
When Palpitine is talking to Anakin in his office, there is a table at the end of the hall with a large object in the middle, and a gold cup on each side. When they leave the office and are talking in the hall, and a thin purple lamp/object appears on the end of it for a few shots, and vanishes whenever seen from then on.
When Mace Windu and Palpatine fight, Windu backs Palpatine into the corner of the window. Note how close Windu is to Palpatine the whole time. Then from Anakin's perspective, Windu takes a few steps toward Palpatine, his saber pointed at Palpatine. When we saw it from the earlier perspective Windu never took those three steps toward a stationary Palpatine.
In the scene where Plo Koon gets blasted by his Clone Troopers, the exterior shots show he is in an Episode II starfighter (closed/pointed bow, no small rear window on cockpit canopy- best seen as the Emperor gives the order), yet the interior shots of his cockpit show he is inside an Episode III starfighter (forked bow, small rear window on canopy- same as Obi-Wan's starfighter).