Choosing lenses for your glasses is an arduous task if not a frustrating one. The problem is exacerbated by the fact that you only get the final product when you collect your eyewear from a certified optician.
Fortunately, you don’t have to risk making the wrong choice anymore. Here are some invaluable factors to consider when choosing:
This is one of the most misunderstood aspects of eyewear and a major cause of wrong choices. The material you choose affects your vision and life of your eyeglasses. Main materials include:
Glass: These offer exceptional optical clarity, scratch resistance and an anti-reflective coating adheres perfectly. Nevertheless, they have a downside in their delicate nature and heaviness. Glass easily cracks and breaks thus making it an expensive option.
Plastic: These were introduced in the 1940s by a California-based company. They are made from lightweight plastic polymer C39 and offer good optical quality, shatter and crack resistance. However, they require a scratch-resistant coating.
Polycarbonate: Are hailed for impact resistance, which is 10 times more than the other materials, lightweight quality, 100% UV resistance without a special coating and thinness. However, they require scratch-resistance coating and require anti-glare for better vision.
Others materials include aspheric and NXT though they are not common in day to day eyewear.
FDA regulates minimum centre thickness in both concave and convex glasses. However, your optician will be able to determine their shape without going against the regulations to ensure your vision is not worsened.
Type of Lenses
These vary in type. You can opt for single-vision or unifocal that provide vision correction for a given distance. Double vision also known as bifocal models, offer two different corrections while the more holistic progressive vision type behave like bifocal ones but offer an invisible boundary line.
To get aesthetically appealing glasses, you should go for an aspheric design with a gradually changing lens curvature from the centre to the edges. They avert magnification of your eyes while also improving optical clarity in peripheral vision.
Index of Refraction
This technical detail implies the ratio of speed of light in a vacuum divided by the speed of light in your glasses material. It is all about how efficient your eyewear will be. The higher the refractive index of the material, the less the material required to bend light. This means a higher refractive index translates to a thinner more appealing and efficient product.