Why don't vision professionals write prescriptions for glasses for people with presbyopia to allow them to focus at distances greater than 6 meters (20 feet)? The difference between focusing at 6 meters and 100 meters is about 0.2 diopters. My vision is corrected to 6 meters with -4.75 diopters. Road signs, especially at night, don't come into sharp focus for me until I'm maybe 30 feet from the sign. I would like lenses with -5.00 diopters but all the professionals say they only test and prescribe for correction to 20 feet. Why is that?