I ordered and received 3 sets of reading/computer glasses.
In most stores, 1 diopter readers are the weakest you can find.
I googled, ordered and received .25 and .5 dipoter glasses from back East, the Canadian store for the American product.
These worked fine, with the .5's the best.
Then I went to an optometrist store here in town and ordered a pair of .75 dipoter readers. These work perfectly for iron sights.

Both sights are good with the front being VERY sharp. The target is a bit more blurry, but I still hit well. The centre of the blurry edge target is easy to hit with sights you can see.