GlassesShop.com invites the authoritative eye specialists to answer these questions that everyone should know so that more and more people can understand them.

1 What is refractive index?
Refractive index is the ratio (N) between the light speed of travelling through the air and that of travelling through the lens. The higher the refractive index is; the thinner the lens would be.

2 The safe central thickness of lens (International)
Resin: 1.0MM    glass: 0.7MM
Zeiss (a brand of glasses, has its own standard)
Resin: 1.2MM   glass: 1.5MM

3 What is the relationship among Abbe number, dispersion and refractive index?
The higher the refractive index is, the lower the Abbe number is and the larger the dispersion is.

4 What are the refractive indexes of eyeglasses lens?
1.523    1.61 (Zeiss only)   1.7  1.8  1.9

5 What are the refractive indexes of resin lens?
1.499   1.56    1.61    1.67    1.701    1.74

6 What are the techniques of the resin lens?
(1) Harden
(2) Apply antireflection coating (FGMC)
(3) Apply UV coating
(4) Anti-irradiation coating (EMI)
(5) Dye

7 What is the polarized lens?
Only the light comes from one direction can travel through the polarized lens. Just as shutter, the polarized lens can filter a part of veiling glare, which makes the light tender and reduces glare so that we can see things more clearly and truly. It is especially suitable for fishing and driving.

8 What does it mean by 50 18 35?
means the representation of a box; 50 is the maximum horizontal diameter of eyeglass frames; 18 is the length of center sill; 135 is the leg length.

9 What does the CE on the frame mean?
CE is the Quality System Certification of Europe.

10 What are the advantages of aspherical lens?
(1) The appearance is more beautiful with less swirl grain.
(2) The image is clearer and more vivid, with which people are tireless.
(3) The lens is lighter and thinner.
(4) The field of view is wider.

Please post your answers and go to GlassesShop.com to see if you are right.