Using the base curve to magnify?

Can you use the base curve of a lens to magnify? I have vision in my
right eye correctable to 20/40, but I have to do a lot of close up
work; I don't want to look like a Borg drone w/ a 2x clip-on
telescope. My prescription in that eye is -11.25 -2.50x178; what base
curve do I need if I want 2x magnification?

On Aug 19, 6:18*pm, douglas <protoman2...@gmail.com> wrote:
> Can you use the base curve of a lens to magnify? I have vision in my
> right eye correctable to 20/40, but I have to do a lot of close up
> work; I don't want to look like a Borg drone w/ a 2x clip-on
> telescope. My prescription in that eye is -11.25 -2.50x178; what base
> curve do I need if I want 2x magnification?

You can't use a base curve to magnify. You can use a near work
prescription and holding things closer however. For example, if you
add +3.00 to your prescription and hold things at 33cm, you will get
some magnification effect.

Best to work with your eye doctor to determine what modification to
make. Measure the distance to the near work and take a sample of the
work to your appointment.

Judy

On Aug 19, 8:10*pm, "Mike Tyner" <mty...@mindspring.com> wrote:
> Base curve does figure into magnification but only trivially. It's very
> difficult to get significant mag from a single element 10mm from the eye,
> without changing the point of focus in some drastic way.
>
> OTOH, spectacle lenses of -1125-250 (10 mm off the eye) will MINIFY by maybe
> 30%.
>
> Contact lenses would not minify.

Yeah, I'm getting fitted for a contact lens when I see my
ophthalmologist and optometrist at the end of the month.
>
> Instead of trying to magnify, I'd recommend using a contact lens to
> eliminate the minification you get with the spectacle lens. That would
> amount to 30% mag, then another ~5-10% from wearing a +200 reading lens. In
> effect you've built a Galilean telescope that focuses at 18".
>
> But again this assumes you actually _use_ the eye we're talking about.
>
> If you have 20/40 amblyopia it's much more important to work with the other
> eye.
How do you know I have amblyopia?
>
> -MT

On Aug 19, 10:52*pm, Salmon Egg <Salmon...@sbcglobal.net> wrote:
> In article <9aGdnVxhbds2IxHXnZ2dnUVZ_sqdn...@giganews.com>,
> *"Mike Tyner" <mty...@mindspring.com> wrote:
>
> > Base curve does figure into magnification but only trivially. It's very
> > difficult to get significant mag from a single element 10mm from the eye,
> > without changing the point of focus in some drastic way.
>
> You can get magnification from strong positive lenses close to your eye.
> Older machinists and other such people do it all the time. I use flip
> lenses or high power (diopter reading glasses. Such lenses, however, are
> useless for ordinary getting around. To get the magnification, you have
> to move the object close enough to your eye so that it is in focus on
> your retina.
>
> Bill
>
> --
> Private Profit; Public Poop! Avoid collateral windfall!

So I have to ask my optometrist to fit me w/ a 2x telescope?

Do I have "low vision" in my right eye?