Shooting glasses and Diopters - the theory please

[GeraldS1]

Never tried a diopter and not sure how it works and what it does and how beneficial it really is. I have seen some ISSF shootoff vids and some guys wear nothing (on their faces) and others have these Knobloch style glasses.
I am right eye dominant and have shot a lot of IPSC with both eyes open so I dont think I need the left eye blanking plate.
I thought the diopter was for older guys and their fading eyesight but then you see that indian teenager with one.? again, not knowing what it actually does.
Now maybe its because I am new at the game, but what I like about 2 eyes is I can catch where my eye ball is focusing by how far apart the 2 blurry targets are in my vision, and of course how un-sharply-focused the front sight becomes. - is this wrong/bad/irrelevant?

Comments appreciated, thanks

[Azmodan]

made a short video about this topic: https://youtu.be/CG80zhOJ5vc

[MikeMargolis]

I use Knobloch glasses with my distance prescription, and an iris for my right eye and a blinder for my left eye.

The iris helps me to keep my head in the perfect position, and to focus ONLY on the target, as I can literally see nothing else.

The iris also increases depth of field if you're using iron sights. I use a red dot so that doesn't matter to me.

I bought a killer pair of Knobloch's on ebay for about $125 and added my prescription lens for about another $75. Worth every penny.

[Rover]

To try to keep this simple: If you are using a Red Dot sight, and have good distance vision, you focus on the bull. Don't try to follow the bouncing ball.

If the dot is flary or not round, you need correction for astigmatism. If you are nearsighted, you need distance glasses. Both eyes open is fine.

For iron sights: you still need astigmatism correction, but focus from your glasses needs to be on the front sight. While a iris WILL increase depth-of-field, that is not what it is for. It's to keep a uniform "pupil" because vision changes at different light levels. You might need a blinder for your other eye. (Scotch tape?) Don't even THINK about bi or varifocals!

[GeraldS1]

made a short video about this topic: https://youtu.be/CG80zhOJ5vc

Thanks all. Just what I wanted to know