Trains Eye

Trains Eye
Can anyone tell me how I can train my left eye to close, without losing my right eye open?

I'm in the army and rifles SA80 we use can not be dismissed given, I should be able to close the left eye so you can look at low vision correctly. I can not wear a patch over one eye that does not is useful during operations. Can anyone help?!

Instead of trying to close the lid attempts to flex the muscle check up on sleep.