Re: Change in lens power with distance
- From: otisbrown@xxxxxxxxxxxxxx
- Date: Wed, 20 Feb 2008 05:46:44 -0800 (PST)
Dear John,
A lot of the "difference" depends on how the minus is prescribed.
You are probably correct that your accommodation (stop-to-stop) is
limited,
but you do have "depth of field". In bright light, that can be from 1
to 1.5 diopters,
depending on aperture.
But I would talk to your OD about this issue. He can give you
slightly
stronger minus lenses if you want that additional sharpness of vision.
A am certain he will be willing to accommodate you (no pun intended).
Otis
On Feb 20, 2:53 am, John O'Flaherty <quias...@xxxxxxxxx> wrote:
I wonder if someone could help me understand something about glasses.
I am 62, myopic, and don't think I have any accommodation to speak of.
My prescription is about -2,-2.25, averaging in the astigmatism.
When I got my eyes checked, I mentioned that I wanted a special pair
of glasses to watch TV, at a distance of 11 ft. (3.35 m), because I
found my old glasses blurry at that distance. I was told that the
distance of the eye chart was 11 feet, and that was taken as
equivalent to infinity. My new glasses seem ok at 11 ft. for watching
TV, but not as good outdoors at infinity.
Is it true that going from infinity to 3.5 m, to maintain perfect
focus, the negative power of the glasses would have to be reduced by
1/3.5 m, or about 0.3 diopters? If true, wouldn't this be a
significant difference in sharpness?
--
John
.
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- Change in lens power with distance
- From: John O'Flaherty
- Change in lens power with distance
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