Dear all, You may be subject to marketing pitch to order your glasses in higher index lenses because it "will look nice" will "fit better in your frame" etc. Do not be fooled. Here is a community service info from me, posted from another thread I have answered a question of someone (by the way, I am not an optician!):
I found one which is freely available without such: http://www.opticampus.com/tools/thickness.php Lets assume the following perscription: R-Sph: -4.5 R-Cyl: -1.25 R- Axi: 17 You need fill in the dimensions of your glasses as well as perscription and material. Note that the Poly used by Zeni is already quite high index at 1.57 vs. the regular CR-39 which is only 1.49. As an example of the above, for the frame someone picked from Zenni at: I bought http://zennioptical.com/cart/product.php?productid=810&cat=3&page=1 (very important to consider the frame since the lens curvirture changes with the dimension of the frame and such is needed for the above calculator), i.e. Eye (or lens) width is 48mm (highest lens dimmension since width is usually bigger than hight in glasses...), bridge 21mm and use of Poly or 1.67 lens material we get: For above frames and perscription, the lens thickness with the 1.67 comes to: 1.6mm in the center and 5.6mm at the edges. With the poly its 1.5mm center and 6.1mm edges, not even 1mm difference at the edges (actually just 0,5mm diff for edges and 0.1mm diff for the center...!). Do not waste your money for the 1.67 index thinking its very thin and better...its not always so and needed. I don't know Zenni or other online or B&M shop asks you to order in 1.67 when you have small prescriptions as above, in which case this is not right for your case or if it will be you whom decide such on your own.. in which case.. its OK as the sales pitch from the B&M stores kept working on you but you wont see a difference and you will wonder if you even got the 1.67 index.. :-) Hope this is of use and Ira can collect this info and add it to the main place for reference... :-) Cheers! Cheap --~--~---------~--~----~------------~-------~--~----~ 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 -~----------~----~----~----~------~----~------~--~---
