On Jun 4, 4:41 am, clarity <[email protected]> wrote: > I think you are trying to learn too much about your glasses and you > are over analysing, and you have ended up missing the point entirely > by attempting understand all this by yourself with no qualified > optician to help you reach these strange conclusions!! .You dont need > to try and find a frame that has the centre near the centre of your > pupil!! The lenses are centred.Why do you think they even take a PD? > - to put the optical centre right on it!!
Thank you for helping me to sharpen my thinking about this, though your harsh rhetorical style would normally tend to produce the opposite effect. There are very good reasons for having the optical center of an eyeglass lens near its physical center: 1) Minimize the thickness at the outer edge of the lens 2) Reduce chromatic aberration by minimizing the difference in thickness between the thinnest and thickest part of the lens 3) Increase the size of the optimal viewing area. (Otherwise, part of that area is beyond the inner edge of the lens.) --~--~---------~--~----~------------~-------~--~----~ 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 -~----------~----~----~----~------~----~------~--~---
