Many different types of materials can be used in your eyeglasses, such as glass, plastic, and polycarbonate. Each of those materials gives a different type of clarity in your vision, and clarity is measured in a value called ABBE value. Each material also has an index value which also shows the thickness of the material – the higher the index the thinner the material.
Glass: This is the original material used for eyeglasses and it is still considered the material with the highest clarity. The downside to this material is that it can crack if you drop your glasses, and it is on the heavier side. Glass has a high ABBE value of 58 and comes with multiple index values (1.5, 1.6, 1.7, and 1.8). The only downside to having a thinner lens is that the ABBE value does decrease.
Polycarbonate or Poly: This is a very lightweight material – it is flexible, and impact-resistant. The downside to this material is that it scratches easily and has the lowest clarity value of all the materials. Poly has an ABBE value of 30 and a single index value of 1.586. If you are looking for clarity in your vision, this material is not for you.
Plastic or CR39: CR39 has come a long way; this material is probably the most commonly used material for glasses nowadays. CR39 has clarity equal to glass, more scratch resistance than poly, it is lighter than glass, and it comes in multiple indexes for thickness. CR39’s ABBE value is the same as glass, which is 58, and the index value is 1.498 (1.56, 1.6, 1.67, 1.74). Once again the higher the index value the lower the clarity.
When it comes to our eyes a natural ABBE value is around 45, when we choose lenses for our glasses, we want something either close to that value, or higher. If you are unsure of the material you should choose for your glasses, feel free to contact us and we would be more than happy to evaluate what would be best for you.
Tim Mak, Licenced Optician. EyeTech VisionCare.