Thanks John, that helps.
But I instinctively feel somewhat uncomfortable imaging one eye being subjected to particular viewing conditions totally different from the other one.
How the eyes can acomodate such conditions ? Don't you feel a kind of incovenience seeing by one eye as usual whilst the other one is subjected to night vision view ?
Since it is in total darkness the other eye sees nothing. It's like you have a patch on. Actually vision is quite relaxed. Once you experience it you will wonder what all the fuss was about. John Berry