Mervy,
I'm in the same boat as you.
What I do is wear the reading specs to get a clear image of the open sights and let the target blur. Even like this I can put a bull in the paper at 10 metres. Made a stupid mistake with a red dot sight. I took it back to the shop complaining that it was a blur and the guy pointed out that I was wearing my readers - doh. Took them off and it was fine. They had worked with the open sight but not with the red dot.
Good luck, and hope you find a way.
Best wishes, Alex.