As we age our eyes loos the ability to "accomodate" that is focus up close and towards infinity. At 60, my accomodation is fairly terrible.
So, I have a pair of bifocals for driving, the upper lens is focused on infinity so I can see the road, the bottom lens is focused at 3 feet so I can see the dash.
I also have a different pair of bifocals for billiards, the upper lens focused so I can see between 5 feet and 10 feet, the lower lens is focused at 2.5 feet to 6 feet. So I can see the cue-tip and CB through the lower lens and I can see the OB and pocket through the upper lens.
It helps, a LOT.