OnlineDoc, Correct me if I am wrong but didn't the switch from plus to minus cylinder occur at about the same time that the switch from glass lenses (which were usually custom ground so the cylinder had to be added to the sphere correction) to plastic lenses (which were premolded with base prescription built in and then finished on the lathe which cut out or subtracted the cylinder correction)? I can remember some of my old plus cylinder precriptions from about 30 or so years ago when I wore case hardened glass lenses that and my minus sphere was about a diopter or two more than it is now (which coincides with the strength of my cylinder correction).
On Sep 22, 2:57 pm, Bjalf <[EMAIL PROTECTED]> wrote: > On Sep 22, 7:18 pm, "Chuck Knight" <[EMAIL PROTECTED]> wrote: > > > Frankly, I'm confused too. I've always been told that the combined total of > > the sphere and the add equals the reading prescription. > > He also changed the + cylinder values to - cylinder values. When you > do that, you apparently have to adjust the sphere values in addition > to changing the axis values. > > Still, the numbers don't really add up. How did this: > +2.75 +0.50 x 010 > +2.75 +0.25 x 005 > > turn into this? > +3.25 -0.50 x 100 > +2.75 -0.25 x 95 --~--~---------~--~----~------------~-------~--~----~ Check us out at the oft-updated http://www.glassyeyes.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 -~----------~----~----~----~------~----~------~--~---
