Well, unfortunately the calculations are neither linear, nor constant for
everyone. The rule of thumb is that a computer prescription, which is
approximately arm's length (a 28" distance is believable) requires an ADD
value of 1/2 your normal ADD value. BUT, that's just a rule of thumb. The
exact adjustment differs for everyone, so I usually suggest the empirical
method.
Hope this clears things up...
-- Chuck Knight
P.S. Don't forget to adjust your PD inwards...
On Wed, Oct 20, 2010 at 4:31 PM, Greg <[email protected]> wrote:
> That's a useful suggestion, but my question concerned how to calculate
> the ADD value,
> rather than determining it empirically.
>
> On Oct 20, 6:16 am, Chuck Knight <[email protected]> wrote:
> > Go to your local store, probably WalMart or similar, and be sure to wear
> > your regular glasses. Then, while wearing your regular glasses, try on
> the
> > standard readers by placing them in front of your regular ones.
> >
> > The value of the reader that works best for you at the desired distance
> is
> > the ADD value you need.
> >
> > -- Chuck Knight
> >
> >
> >
> >
> >
> >
> >
> > On Sat, Oct 16, 2010 at 7:04 PM, Greg <[email protected]> wrote:
> > > How do you calculate what sphere additional value to specify if you
> > > want your monovision glasses to work best at x distance --- e.g., at
> > > 28" from a computer screen? I've ordered three pairs of glasses to
> > > use with my computer, and for the last two, I added 0.75 to the SPH
> > > values of my prescription (which worked well), then 1.00 (which worked
> > > a little better). It's just been guess work, so far, since I've never
> > > seen a formula that would give an analytic approximation. At my last
> > > eye exam, I asked my optometrist what values I should use for my
> > > computer screen, and she told me to add 1.50 assuming my computer
> > > screen was 22" away. Maybe that was right, but how do I know? (Just
> > > going on intuition, I decided 1.50 was too high, and I ordered some
> > > glasses from Zinni using an add value of 1.00, and those seem to be
> > > okay.)
> >
> > > --Greg
> >
> > > --
> > > Check us out at the oft-updatedhttp://glassyeyes.blogspot.com!
> >
> > > You received this message because you are subscribed to the Google
> Groups
> > > "GlassyEyes" group.
> > > To post to this group, send email to [email protected]
> > > To unsubscribe from this group, send email to
> > > [email protected]
> > > For more options, visit this group at
> > >http://groups.google.com/group/glassyeyes?hl=en
>
> --
> Check us out at the oft-updated http://glassyeyes.blogspot.com!
>
> You received this message because you are subscribed to the Google Groups
> "GlassyEyes" group.
> To post to this group, send email to [email protected]
> To unsubscribe from this group, send email to
> [email protected]
> For more options, visit this group at
> http://groups.google.com/group/glassyeyes?hl=en
>
--
Check us out at the oft-updated http://glassyeyes.blogspot.com!
You received this message because you are subscribed to the Google Groups
"GlassyEyes" group.
To post to this group, send email to [email protected]
To unsubscribe from this group, send email to
[email protected]
For more options, visit this group at
http://groups.google.com/group/glassyeyes?hl=en
