February 07, 2008
As the image to the right shows, the layout of the different focal areas on a progressive lens introduce some interesting geometry into the lenses structure. In an effort to produce a lens that mimics natural, un-corrected vision, without lines, the optimal corridor of vision can be rather small. Not to mention the size of the near vision portion at the bottom of the lens. When I ordered my new lenses we had the lens upsized to the largest lens the frame would support; I cannot believe that I would be able to wear glasses with a smaller progressive lens at all.
The portion of the lens that I believe is giving me trouble is the unlabeled portion on the image; the part to the left and right of the intermediate vision corridor. What I want in my lenses are what is known as an executive, or Franklin, bifocal.
(Images are from All About Vision.)