In the years past there was just one eyeglass lens material:  glass.  Today, there are a multitude of materials and no one material can be considered superior in all aspects.

The following is a list of the most commonly used materials. The numbers in the names of the plastics indicates the index of refraction for that material (how well the material bends light).  Generally speaking, the higher the index of refraction, the thinner a lens will be for a given prescription.  Next to each material is a listing of the pros and cons of that material.

Glass - The first eyeglass lens material
Pros: Exceptional optical clarity, naturally scratch resistant
Cons: Heavier than all other materials, can be broken which may create a safety issue, its decline in use has caused its price to spike upward, cannot be cosmetically tinted

CR-39 - The first plastic eyeglass lens material
Pros: Lighter than glass, good optical clarity, can be cosmetically tinted, economically priced
Cons: Not as scratch resistant as glass, index of refraction less than glass, not a good material for drilled rimless

Trivex - One of the newest lens materials
Pros:  Light weight, optical clarity comparable to glass, very good impact resistance, can be cosmetically tinted, the best material to drill or groove
Cons:  Index of refraction not much better than CR-39, more expensive than CR-39 or Polycarbonate

Polycarbonate
Pros:  Lighter than glass and previous plastics, superior impact and chipping resistance, provides a thinner lens than all previous materials, can be drilled or grooved
Cons:  Compromised optical qualities, easily scratched without a hard coating, poor tinting qualities, poor resistance to chemical damage

Plastic 1.54 and 1.56 - The first “high index” plastic materials
Pros: Lighter than glass, can be tinted, provides a thinner lens than glass and CR-39
Cons: Optical clarity inferior to glass, not as scratch resistant as glass, more brittle than CR-39 (edge chipping), not a good material to groove or drill

Plastic 1.60 - 1.67
Pros:  Good optical clarity, provides a thinner lens, can be drilled, can be grooved, can be tinted 
Cons:  More expensive than other materials, not available in all progressives and photochromics

Plastic 1.70
Pros:  Provides the thinnest lens, can be drilled, can be grooved, can be tinted
Cons:  The most expensive lens material, not available in all progressives and photochromics

As you can see, no material is considered to be the best for all applications.  As a general rule, if you consider your existing lenses to be thick it is best to choose a higher index material.  If your activities suggest eye protection, Polycarbonate or Trivex is by far the best choice.  If you have choosen a drilled rimless frame, Trivex is best suited.  If your frame is a string rimless, consider Polycarbonate, Trivex, or Plastic 1.60 - 1.67.

E-mail support@sharpglasses.com with your prescription and frame choice, and we will help you to select the best material for you.