To give me a crisp front sight, I use the stick-on bifocals (+1.00) you can get from Hidalgo Supply and other places. I cut them to fit on the upper left portion of the right lens of my shooting glasses (my dominant eye) so that I'm only looking through it when I'm shooting with my head "ducked" slightly. This allows me to see a crisp front sight with my dominant eye, but the effect on the target (additional fuzziness) is minimal because the left eye is not looking through the additional magnification.
I actually learned about using only one stick-on bifocal by accident. I bought some new sunglasses and wanted to try them out before the new stick-on bifocals arrived. I took the bifocal off of the left lense of a pair of shooting glasses and tried it on the new glasses. I was amazed how much better it worked. The best things about this approach is that you can put the stick-ons on any glasses and you only have the extra magnification on the dominant eye, which prevents the target from being significantly more blurred.
Since I am farsighted and use a (+) prescription, I don't know if this method would work for someone who is nearsighted using a (-) prescription. If you are nearsighted and still use reading cheaters (all of them are (+) prescriptions), then this may work. It would be helpful if someone who wears a (-) prescription would try this and report their results.
I hope this helps.
Chas.