Thinner & Lighter Lenses
Today there are many different types of thin and light lenses. Generally the thinner the lenses the more they cost. As the high index materials can loose up to 15-20% of the light off the surfaces, most thinner lenses come with an anti-reflection coating and 100% UV protection as standard.
Due to increased technology and research in the high index plastic lenses, the days of high power prescriptions only being made in hi index glass is now almost a thing of high power prescriptions only being made in hi index glass is now almost a thing of the past.
Considering that standard plastic lenses are 50% lighter than glass and safer, all but the really high power prescription lenses can utilise the new thin plastics for their incredible lightweight characteristics for general comfort on the nose and safety.
The obvious benefits are:
- Comfort- they are so light that you can say good-bye to those large indentations on your nose
- Plastic lenses can be made approximately 50% thinner and 40% lighter than standard plastic lenses.
- The overall appearance of the frames and lenses is greatly improved due to the frame being more of a feature than the lenses, especially when most come standard with an anti reflection coating.
- As the material is thinner and flatter, there is less magnification to a plus lens and a reduction in the “gold fish bowl” effect. A result that certainly attributes to giving your eyes a more natural appearance.
- A far safer option to glass. They are not necessarily unbreakable, but to do so is very unlikely. Hence, for people with only good vision in one eye, it seems only natural to better protect that eye in case a freak accident happens.
Here is a list of the main lens materials available today. The higher the refractive index the thinner the lenses will be. In plastics the weight generally gets lighter, whereas in glass the material is denser and therefore heavier.
Glass (standard minerals=1.523) then 1.7, 1.8, 1.9
Plastic (standard CR39=1.5) Then : 1.55, 1.6, 1.67, 1.71, 1.74
The right lens material for you depends a lot on the prescription, frame size, frame type and pupil distance (P.D =the distance between your eyes).
Generally:
For short sightedness (-ve power lenses) – the bigger the frame the thicker the lenses at the edge . Hence, small frames cut away more unwanted lens thickness resulting in far thinner lens edge.
For long sightedness (+ve power lenses)- the bigger the frame the thinner a lens can be made for you. If however you use a standard stock lens, the thickness at the center can be quite noticeable, the reason for having the lens surfaced for you to minimum thickness
