How do the actors see through visors (bug eyes)?

[KamenRiderCyber]

that helmet might look solid but im sure those eyes are actually clear.

my question is how does one see with a helmet like Ryuki, Knight or Diend?. not only do those have those eyes but they also have the grates in front of the eyes

Remember that the "grates" are actually closer to the eyes than what can be shown using a TV can. It's about the same as a jousting knight's helmet in the late 16th century.

That could make for an interesting game, of course: spotting the eye-slits in the "hero" helmets of the various main and secondary Riders. (For W and OOO, as an example, those slits are below the bug-eye windows, and triangular.)