The "Monster" acts as the eye of the Island. When Locke tells Jack that he has looked into the "eye of the Island" it's implied that he is referring to his first encounter with the smoke monster. Later when Eko encounters it, it seems to 'look' at him, and see some of his memories.
The shot of the eye appears after a "rebirth" of the character. Sometimes literally, like Locke in the mass grave ("Through the Looking Glass, Part 1") or figuratively, like Claire after the car accident that killed her mother.
Many of the characters in the show are deceptive. When an episode opens with their eye, its generally an indicator of an introspective on that character. These are the only times we should trust the actions and/or intentions of these characters, as their motives in an episode that isn't introspective to them may be uncertain.
Jack's eye opening at the beginning of the series is shown again in the final episode, "The End," implying that it was an important event. The emphasis seems to hint that this was Jack waking up into a new plane of consciousness Third eye.--Sammerjammer 04:21, October 9, 2010 (UTC)