In terms of lightweight, aesthetics, and usability, nonspherical surfaces are superior to spherical surfaces; In terms of price, nonspherical surfaces are generally higher than spherical surfaces. In addition, nonspherical lenses have many functions and a wide range of applications.

When you don't know how to choose the cheapest eyeglasses online, choosing a nonspherical surface usually won't go wrong. To exaggerate, if you're going to get spherical lenses, why don't you cut a glass ball and wear it on your eyes?

Generally, a new type of glass is ultra-thin, ultra-thin, or ultra-thin, but when you look at it, the price is ultra-high, ultra-high, or ultra-high. At this point, I will think about the principle of ultra-thin lenses and why they become ultra-thin.

Let's talk about thickness first. Generally speaking, the refractive index is used to describe thickness, and the higher the refractive index number, the thinner it is. Will there be a significant difference in thickness or price?

Is it better for lenses to be thinner and more expensive? We usually think that expensive ones are better, but when it comes to choosing lenses, is that the case?

I followed this idea and searched around, and I found some things that eyewear store staff usually wouldn't be able to tell us. Of course, I think it's also something we must understand when purchasing discount eyeglasses online.

Later, I found my previous optometrist and told him about what I found, and he admitted that the Abbe number of my lenses was not higher than before.

What is Abbe's number? Abbe number is a very strange name, right? But anyway, all you need to know is that it is a physical academic concept.