As a side note with the eyes closed
bit, in SERE training they told us that it can take up to 45 minutes to fully acclimate to dark from bright light. But if you're in a situation were you have you start seeing well in very low light and you keep one eye closed in bright light your "night
vision" will
return at an amazingly fast rate. Don't have any links to back it up but they tended not to lie to us.