An aid for older eyes,

[madcaster]

seeing the post on yellow shooting lenses made me remember an article I read in a muzzloading magazine,that if you use a piece of black tape on your glasses with a small hole cut into the tape,that it would help you with iron sights.
No mention was made of extended shooting time though...[smilie=1:
I hope this helps someone in our great sport.

[NVWalt]

I use a piece of blue tape with a hole from a 1/16 inch hole punch in it and have been using it for years with open sights in competition and it works as well as my Merrit loop I had at one time and considerably cheaper....Walt

[montana_charlie]

Peep sights (especially tang sights) have that same effect...
CM