Omnioculars

Being a proud member of the four eyed community it has begun to creep into my thoughts that I too may some day need to wear bifocals or, even trifocals in order to see clearly at different focal points.
It seems an awful shame to me to have a large portion of the vision I now enjoy blocked out by the portions of my glasses needed to see either close or far away, so why not make adjustable lenses that are round and slightly flexible.
By alternately tightening or loosening the diameter of the frame the lens will protrude more or less and give the wearer an unlimited range of prescriptions to pick for a given task.
I know that it is not good for your eyes to wear a prescription other than your own for any length of time, so the turn screw on the side of your glasses which changes the focal point should have a tactile feel for where the proper prescription of each lens is located; set by the optometrist by pushing inwards on the turn screws. Future settings for close reading or far viewing could be set by the wearer as long as the original prescription can be found easily by feel.
By having control of two lenses per side, I think that a form of weak binoculars could be created from your glasses, allowing you to see farther than with unaided twenty twenty vision.