.. when you have been using superior Eagle’s Sight to block an action (after ignoring the normal prey, predator or target restrictions for blocking actions), and the acting vampires continues the action after a successful block (with cards like Form of Mist or Crypt’s Sons), you need another way of blocking the action again. In other words, Eagle’s Sight is only good for one block attempt. But since you cannot play the same reaction card twice during an action, you (most likely) cannot block the action any longer.
The reason for this is the card text, which states the card allows the reacting vampire attempts to block the current action despite of the usual restriction. The same applies to Falcon’s Eye at superior Spiritus with the same card text. Anneke on the other could block again in the situation described above, because her card text is sort of permanent, allowing to break the usual block restrictions multiple times during an action.