Choosing the Wrong Sunglasses Can Bring the Eye Great Harm

While emboding the self-personality and beautifying the appearance, a pair of best sunglasses can also attain the purpose of protecting the eye. However, sometimes it may deviate the initial intention when we choose the wrong one.



It is wise to wear a pair of sunglasses when you are exposed to a large area of snow, clouds or water. Human beings can not survive without the sun, but the extremely strong sunlight can damage the eyes. It can cause acute damage to the eyes, such as snow blindness (also known as daylight ophthalmia). Snow blindness is caused by reflection of a large area of snow from sunlight (clouds, or calm water), making the outer layer of the eye burned by ultraviolet radiation. The typical symptoms are eye smart, dryness, tearing, foreign body sensation gravel, skin redness, conjunctival hyperemia, edema and so on. The extremely strong sunlight can lead to chronic eye diseases such as cataracts, macular degeneration, pterygium, chronic conjunctivitis, ects. A survey shows that the incidence of these types of diseases is significantly higher in high altitude areas than in low ones, because of the strong ultraviolet in high-altitude areas. Therefore, wearing sunglasses scientificly can not only prevent eye burned acutely from ultraviolet radiation, but also take precautions against disease mentioned before.
As we all know that electromagnetic of 100-400nm wavelength is called UV. The 315-400nm wavelength electromagnetic is known as ultraviolet A, which is one of the causes of cataract. The 280-315nm UV is UV-B, which is one of the factors that causes acute keratoconjunctivitis. The UV below 280nm C is extremely harmful for growth and development of animals and plants on the earth. Fortunately, most of the ozone layer is filtered out. In recent years, with the deterioration of the survival environment, the ozone layer is destructed and UV-C is becoming white. While reducing the transmittance of visible light, the sunglasses can block off ultraviolet rays to protect the eye. A high-quality sunglass can either resist UV completely or maintain a relatively high visible light transmittance. But the sunglasses on the hawker stalls are not ideal to prevent UV. Some UV-A`s transmittance is up to 40%, while the visible light transmittance is below 10% or even 4 %. And some are abnormal absorption, imagining when visible light is partially blocked and the pupil is enlarged according to the pupillary light response, which bring much harm to the eye. Therefore, cautiousness and clear knowledge of the product you choose is needed when you select sunglasses, paying attention to the product trademark, origin, name and address and the signs of UV or UV400 (UV is anti-UV below 380, and UV400 is anti-UV below 400nm).

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