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OK, for fun. Take your glasses off and find a comfortable distance and look at the vertical lines. Cover an eye. Bet they might appear at different lengths, some lighter or at different apparent distances. Look at it corrected.
Now turn your monitor or your head 90 degrees and look at them. Bet they are more behaved.
The first is a result of verticle astigmatism which makes:
HELLO WORLD more difficult to see than
Hello world
This might be better:
HELLO WORLD
hello world
I'm still curious as to what distance you can see close without glasses. This should be about 14". The characters might appear distorted, but in focus.
Second, the prescription doesn't tell all.
The optician measures PD or pupil distance. He/she also comes up with a number relative to the pair of frames where to put the optical center and he bifocal.
There is a Near PD and a FAR PD and most opticans will put them the same unless they are way off.
An interesting lens to check out is the iZon lens at
IZON. To me, it's like Lasik surgery on glasses. They, only within the last month or so became available in my area.
Lenses themselves offer some distortions. They have an index of refraction which determines the thinness of the lens.
I'm nearsighted as well and had 3 prescriptions made with the same frame:
Crown glass, AR one side, UV the other, Bifocal
Trivex plastic, inherent UV because of plastic, AR coated, bifocal - same as above
Crown glass, AR one side, UV the other, Hi Bifocal, Focal length probably close to 12". Desisgned for either prolonged close work and using laptop while in bed watching TV.
I was considering a single vision lens at the bifocal strength which I had in the past.
I don't need the bifocals to read, but they provide some relaxation to the eye. As a result, my vision does not change much over time.
When I did my little learning exercise, I did not pay attention to astigmatism because it was of little concern.
Now, I'll get in trouble for this one. With my camera, a ruler and some software, I virtually got the same FAR PD as my optician. We compared notes. I could do better measurements if I had someone else take the pictures.
I'll come back to your questions.
I need the max distance you can see close without glasses. Ignore distortions.