I'm going to put in my usual nonsense.
With minus power lenses, they have progressive BD prism. As a visual aid, envision a six-foot-tall target painted on a wall across the room and the myope standing in front of it, looking at the bull's eye.
The bull's eye will be perceived exactly where it is, in real space, because that's coming through a no-prism section of the lens.
The next ring down will be coming through the lens where there is some BD prism. Let's just say, 1/2^ BD. So the "9 points" ring is going to look higher than it actually is, but only by a small amount.
Light from the "5 points" ring comes through the lens where, let's say, 2^ BD is present. So that ring in the peripheral vision is going to look higher, too, but even more so than just off-center objects, because while the first ring is only slightly displaced, this ring is displaced even more.*
So the net effect is that the inferior field is compressed for a myope.
So what do we want in a progressive lens? Do we want one that is likewise compressed to fit the prism compression, like RM thinks?
Bookmarks