Oh well, might as well put in my two pennorth I suppose! - mostly the same as above though.
My optician explained to me - concerning varifocals, which I use, that the problem with reading (lower half) and distance (top bit) comes about with the shape of modern spectacles, in that they are of a very slim design (top to bottom of the actual glass) and thus the 'halves' are very slim too. Added to this of course with varifocals there is a 'middle' section of glass blending the reading to the distance.
What I do now is to have a pair of varifocals and a pair of 'total' reading glasses (if you see what I mean.) Through doing this for a couple of years now I have also discovered that I prefer to wear the 'just readers' when I am actually reading as well, as I was beginning to find that if I wore varifocals and reading a book I was having to tilt my chin up to be able to read clearly - and this was causing me to often find myself with a stiff neck at the back.
In essence my varifocals are brilliant if I am at say a stitching show and want to see what's on display (distance) and look down at something close (such as the inside of my purse - I do that a lot at these flipping shows!); or if I am in the car and want to look at something distant and then look down at a newspaper. If I intend, however, to have a serious stitching session or a lengthy book-read then I switch to my 'readers only'.
You can only try and see what works for you at the end of the day, but at least it shows that we can all identify and empathise with this issue.
In the meantime - keep eating the carrots!