About 2000 years ago, Seneca, the Roman philosopher looked at his book through a cup of water. The text below the water became clear magically. However, it's about thousands of years later that this principle is used to create the first glasses.
Nowadays, glasses help millions of people with poor vision for the reason of uncorrected refractive errors. The key to understanding the process of glasses working is the function of a transparent medium, like glass, or the eye to make a change of the direction when light passes through.
There are two main refractive surfaces of our eye: the lens and the cornea. Normally, they co-work to refract light in a way that correctly focuses light onto the retina and the vision is given by the layer of light-sensitive tissue at the back of the eye and together with the brain.
However, a large number of people develop refractive errors, which causes refracted light to be focused on part of places, like in front of the retina or behind it. Images become blurry in this situation.
People who have problems with refractive errors can still see colors well as light, but what see are not quite clear and lose details. For those who can see objects near clearly, but cannot see clearly of objects far away are called short-sighted. They. On the contrary, people have long-sighted eyes cannot see close objects clearly.
There are also some people have astigmatism,which causes all things whether they are far or close all out-of-focus and blurred.
With the growth of our age, we may face some new challenges with our eyes.When we become older, the lens of our eyes would become less flexible as before, and they can't change shape at the time when we look at close objects.This is what we called presbyopia.
All symptoms we just talked are refractive errors. Today we can fix them all with eyeglasses or contact lenses.By wearing them, we can refocus light and it strikes the retina accurately. Glasses are still the most popular when one want to see clearly.
Today's glasses have taken many inspiration from the design in 1727( the first glasses have arms to hook over ears), and glasses are much more precise than glasses that time. We can choose all kinds of glasses in different shape or style to show our personality. If you have a problem with close or far vision, there are plenty of eyeglasses at Jim Halo waiting to be chosen by you and help you to see clearly everyday.
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Original Sourse: TED