If you want to buy a pair of prescription glasses, you should consider the lens thickness and the refractive index of glasses. But what is glasses lens thickness? What is the refractive index of glasses? This post will show them. First of all, we will introduce what the refractive index of glasses is.
Refractive Index of Glasses
According to the refractive index, there are a lot of different lens materials. The refractive index is the ratio of the speed of light when it travels through air to the speed of light when it passes through the lens materials. It is an indication of how much light is bent as it travels through the lens. Light is refracted or bent, at the front surface of the lens, then again as it exits the lens.
A denser material bends light more, so not as much material is needed to achieve the same refractive effect as a less dense material. So, the lens can be made thinner and lighter.
In general, the higher the refractive index, the more light is bent by the material and the thinner the lens can be for a given power. A standard index of the lens is 1.5. A mid-index lens of refractive index is 1.6, so about 20% thinner than a standard lens. And a high-index lens of refractive index is about 1.67, and will be 33% thinner than the standard lens. Besides, a lens with a refractive index of 1.74 will be around 42% thinner.
Because higher refractive index lenses reflect about 50% more light than standard index lenses, they are always coated with a multi-anti-reflection coating that will reduce the amount of reflections from the lens surface to less than 1%.
What Glasses Lens Thickness Should I Choose?
In this section, we will show you how to choose glasses lens thickness. Lens thickness will depend on the strength of your prescription, your pupillary distance, the size of the frame and the lens material. Usually, high prescription glasses are thick.
If you have moderate nearsightedness, you should choose thinner lenses at the edge thickness of your lenses will be more visible. If your sphere prescription is between -2.50 and -4.00, the lenses with a refractive index of 1.6 would be an ideal choice. A lens with a refractive index of 1.67 is suitable for sphere prescription between -4.00 and -6.00, and any prescription over that a lens with a refractive index of 1.74 will be more suitable.
So, when you purchase prescription glasses, consider the glasses’ lens thickness also. If you want to get a pair of prescription glasses online, Koalaeye Optical is recommended. It is an online optical store and provides all kinds of eyeglasses, sunglasses and frames. Besides, these glasses are stylish and cheap. If you purchased, the glasses will be mailed to you with great convenience.
To sum up, this post has introduced the glasses lens thickness and refractive index of glasses. If you have and different ideas, share them in the comment zone. If you have any problems with glasses or sunglasses, feel free to contact us via the email service@koalaeye.com and we will reply to you as soon as possible.
