I have one pair of metal frames with a 38mm lens width, and with a -6.25 prescription, the CR39 lenses stick out at most only about 1.5mm from the frame. The maximum total lens thickness is just over 4mm. Besides the small lens, the thickness was also minimized by having the optical center very close to the physical center of the lens.
On another metal pair with CR39 lenses, with the optical center of the lens closer to the nose (which is very typical), and a higher -7.00 prescription and a 48mm lens width, the maximum thickness is about 7mm, with just under 4mm sticking out from the frame. The edges aren't polished, so I would consider this about a worst-case scenario. It's not that good, but it's not terrible, either. I get almost exactly the same measurements on a frame with a 50mm lens and the same prescription. I see three main factors - lens width, location of lens center, and edge polishing. The fourth factor is lens material, but so far I was only looking at CR39 lenses. On a metal frame with a 41mm "Thin and Light" 1.57 lens and a -6.50 prescription, the maximum thickness is 4mm, and the lens sticks out almost 2mm. The optical center of the lens is somewhat toward the nose, and would be better centered if not for the wide 26mm bridge on this frame. --~--~---------~--~----~------------~-------~--~----~ 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 -~----------~----~----~----~------~----~------~--~---
