Re: Binoculars with Glasses

thunduh@xxxxxxxxxxx wrote:
On Mar 20, 7:25 pm, "Von Fourche" <khonak...@xxxxxxxxxxx> wrote:
Whenever I use a pair of bino's I always take off my glasses because I
can't comfortable use them
with glasses on. Plus I always close my weak eye (left eye) and just use my
right eye with the binocular. I can't get both eye pieced to focus equally.

My question is - are there any good, and low priced, binoculars for
people with glasses? Are there any binoculars that I can get that come with
diopter power to match my glasses? I'm getting tired of taking off my
glasses when I want to use bino's. I'm also getting tired of closing one of
my eyes - I feel like I'm getting cheated by not using both eyes. I was
thinking of trying a monocular too.

Thanks!

They way my eye doctor explained it to me. I told him that I had
bought a nice pair of binoculars and that I was adjusting the diopter
but I expected better clarity with the price I paid for the
binoculars. He asked me and I told him that I was not wearing my
eyeglasses because I could not fix on the object that fast with my
eyeglasses on. He said the prescription for my eyeglasses made all
the corrections so that I see clearly. He said that I should have my
eyeglasses on and that I would not have to make any adjustments
(diopter) because my prescription makes all the adjustments. He was
right in that I don't have to make any adjustments and everything is
clear. This is particularily true with people with astigmatism.

I'll explain a little more. An eyeglass prescription corrects each eye separately for astigmatism and near/far vision. That means that when using eyeglasses, the "diopter" adjustment* -- the eyepiece with the +|- marking -- should be set at neutral ('|') with the eyeglasses doing all the near/far correction.

Points to keep in mind: 1) Astigmatism gets worse as the pupil gets larger. That's why it bothers us less in bright light and why dilating eye drops may be used to assess it. 2) The effective pupil is never larger than the exit pupil of the instrument you use. With 8x25 binoculars, it never gets larger than 8/25=3.125mm. (With a microscope, the area of the eye's lens actually used is so small the the eye's astigmatism doesn't matter.) 3) Some eyeglasses make using binoculars especially difficult. Variable-focus ("no-line") bifocals can be especially tricky. Usually, there is an unchanging region near the top that works, but looking straight through the middle will likely blur the image. I use executive (line all the way across) bifocals, with the dividing line just below center. If the line is in the wrong part of the field, I actually see a double image. I'm considering having a distance-only pair made for use with optical instruments of all kinds. (Reading-only would work as well, but I can get dollar-store reading clip-ons.) People whose near- or farsightedness is so severe that the focus range of most binoculars can't accommodate it are stuck with eyeglasses or extra corrector lenses attached to the eyepieces.

The upshot: if you have only moderate astigmatism and find the combination of eyeglasses and binoculars irksome, use binoculars with an exit-pupil about 2.5 to 3 mm. The chances are good that astigmatism won't be a problem. (My small pocket-size Audubon 8x25 and my Canon IS 10x30 both fit.) Just remember that the differential focus matters, and needs to be readjusted when the binoculars are passed from person to person. And forget about good seeing in dim light. :-(

Jerry
________________________________
* Do me a favor: call it a differential focuser.
--
Engineering is the art of making what you want from things you can get.
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.

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