Yes, its a problem in my bifoculs as well.../ or progressive lenses....
So I wear shooting glasses....that allow me to see the front sight clearly. One lens is cut for the right focul length to see the front sight clearly - the other for distance so target isn't too fuzzy....
DeCot HyWyd is my preference for shooting glasses -- changeable lenses to allow for different light conditions ( at indoor ranges, I shoot a light gold, light yellow lens color).
http://sportglasses.com/
If you can't see the front sight clearly - you won't shoot your best.