The sun produces many kinds of lights. To accept some sunlight everyday is very important for the health. Sunlight is especially important for kids and those who work underground such as miners. Most peopledon’t get enough sunlight each day, but when you are going to face long time exposure to sunlight, sunglasses become requisite. The lights that can harm the eyes are UV rays (ultraviolet radiation), bright or intense light and blue light. There are two kinds of UV rays that reach the Earth’s surface: UVA and UVB. UV rays can cause or speed up the progress of several eyes diseases and also link to skin cancer. The harm caused by this kind of light happens over a long period of time and cannot be reversed. Blue light is visible light in the blue portion of the color spectrum. Too often exposure to blue light can age the retina and increase the risk of blindness in some people over the age of sixty.
Sunglasses can block some visible light and most of the UV rays. Though proper sunglasses can fend off UV rays and prevent glare, but inferior ones can do harm to your eyes. Actually, if the inferior sunglasses don’t have UV block, then it will be more harmful wearing them than not, because the darkness causes your pupils to dilate bigger. So to choose the correct sunglasses is very important for the health of your eyes.
UV absorption of different kinds of sunglasses
Generally speaking, most sunglasses lenses are UV absorptive to some degree. Lenses made of CR-39R plastic can absorb 88% UV rays; polycarbonate lenses can absorb all UV rays. Cheap sunglasses made of triacetate can only absorb 40% UV rays. Lenses that are made of other acrylic materials have various UV absorptions. To make sure your sunglasses can provide protection for your health, buy them from optical professionals. And you can do some test to make sure the degree of your sunglasses’ UV absorption.
Other factors to consider
First thing is to consider is color. Some people think colors are a personal preference. But they can really influence the performance of the sunglasses under different weather conditions. Generally speaking, black/gray lenses are best for road rides, especially on sunny days; amber lenses are for cloudy skies, and not for bright sunny days; red, rose, vermillion and orange lenses are for cloudy and hazy conditions, and not for bright sunny days; yellow lenses are for early morning fog; blue lenses are best for fashion shows.
Sunglasses are made with different kinds of lenses to meet different needs: polarized lenses can reduce glare by blocking the light that reflects in from water or the highway, therefore they are great choices for those who drive a lot or spend time on water; photochromic lenses can darken into a sunglasses when exposed to UV rays, while show lighter color when you are indoors. But the changes will take up to two minutes. Flash mirror lenses are highly reflective and greatly reduce the amount of light that reaches your eyes.
You can’t tell the degree of UV absorption of your sunglasses from their price, color or the darkness of the lenses. But you can look at the label that tells about the type and the protection. Manufactures that comply with industry standards have grouped their products into three categories: cosmetic sunglasses block less than 60% visible light and UVA rays and 87.5-95% UVB rays, they are only suitable for not harsh sunlight; general purpose sunglasses can block 60-92% visible light and UVA rays and 95-99% UVB rays, they are good for driving and can be used when the sun is so harsh that makes you squint; specially purpose sunglasses are most UV absorptive. They can absorb up to 97% visible light, 98.5% UVA rays, and more than 99% UVB rays. This kind of sunglasses is suitable for prolonged sun exposure, but not recommended for driving.
Since ultraviolet radiation can do damage to one’s health, and low quality sunglasses can do more harm than good to the one’s eyes, so it is recommended to go to an optician or eye doctor’s optical shop to choose a pair of sunglasses that can give you proper protections.
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