Abilities sourced by sight do not require the user to literally see the target with their eyeballs. While that's still necessary in most cases, some creatures may have some sort of "blindsight" that allows them to "see" other creatures even when there's no light in the environment. Nevertheless, these abilities always require that the user have some sort of direct "visibility" of the target akin to seeing them directly. Regardless of how exactly the user sees the target, sight abilities can be used over some range that may not actually be as far as the user can see. For instance, Duel operates by sight, but has a range of 30 feet even though the user may see the target from much further away.