This may have been covered before, but here goes ....
Most of us were taught many moons ago to focus on the sight for an accurate shot, with a quick check on the target for alignment. Again for many of us focus the front blade is very hard (without craning neck to look through progressives or bifocals), and focus on the rear sight for a good alignment is VERY tough if not impossible without optical assist from bifocals. This leaves two choices shoot from an un-natural compromises posture, or shoot with a very blurry sight picture.
Painting the front blade fluorescent green or orange helps some.
I have heard that some use a different technique of focusing on the target and allowing the sights to blur. Now we can easily focus on the target through our regular lenses (or no glasses for some). But can you see the sights well enough for a precise aim.

All useful comments on working with iron sights and aging eyes greatly appreciated. O--O.
Magnumb