In 2007, the slogan of the activity became "finding a slide by slapping on a landslide". In this way, the initiative now includes finding shade and wearing sunglasses to further reduce people's exposure to ultraviolet rays. This emphasizes the importance of protecting eyes (and skin around eyes) from ultraviolet radiation.
Short-term impact
A brief exposure of unprotected eyes to ultraviolet light usually does not produce any symptoms.
However, long-term exposure to ultraviolet rays without eye protection or exposure to strong ultraviolet rays (including the sun, welding arc, snow bed and tanning bed) will cause keratitis.
This situation can be understood as sunburn of cornea (a clear and transparent layer in front of eyes). Ultraviolet rays can kill the outermost cells of the cornea.
After sunburn, severe pain will appear after about 6- 12 hours.
Treatment of photokeratitis includes oral painkillers and eye antibiotic ointment (to prevent the injured cornea from being infected), while waiting for corneal cells to regenerate.
It takes 24~72 hours to fully recover, and then people can be completely unaffected by the complications of photokeratitis.
long-term effect
Repeated exposure to ultraviolet radiation and lack of eye protection can lead to permanent eye damage. Eye diseases caused by long-term ultraviolet radiation include the following.
cataract
In cataract patients, the lens that should be transparent in their eyes becomes cloudy. This will lead to blurred vision and eventually blindness if not treated in time. It is estimated that 20% of cataracts are caused or aggravated by ultraviolet radiation.
Wearing sunglasses is one of the most effective ways to prevent cataracts.
When serious visual impairment is caused, surgery is needed to remove the cataract. In Australia, the total annual cost of these operations exceeds A $320 million.
pterygium
This is a benign hyperplasia of corneal conjunctival tissue. Conjunctiva is a transparent membrane that covers the sclera (the white part of the eye) and generally does not cover the cornea. Although it is not carcinogenic, the appearance of pterygium can lead to chronic irritation, redness and inflammation.
Pterygium will proliferate slowly in a few months or years, and when they cover the pupils, their vision will be blurred. They may also cause astigmatism (incorrect corneal curvature), which will also blur vision.
The treatment of pterygium that is not serious and does not affect vision only needs the lubrication of artificial tears. Pterygium that affects vision may need to be surgically removed.
Similarly, long-term exposure of eyes to unprotected ultraviolet rays is also the main factor leading to pterygium.
Macular degeneration This is a degenerative disease that affects the middle part of the retina (macula) (responsible for central vision). Macular lesions may cause serious vision damage.
The treatment of macular degeneration includes injecting drugs directly into the eyes to limit the deterioration of the disease; But this method can't cure the existing damage.
Although the relationship between ultraviolet rays and macular degeneration is not as obvious as that between ultraviolet rays and cataracts and pterygium, short-wave radiation and blue light (appearing in bright sunlight) will damage the retina. Macular lesions are still related to light.
Therefore, wearing sunglasses plays an important role in limiting the retina from being exposed to excessive light.
cancer
Although this situation is rare, long-term ultraviolet radiation is closely related to the increase in the incidence of several eye cancers. These eye cancers include: squamous cell carcinoma of conjunctiva (squamous cell carcinoma of conjunctiva), intraocular melanoma (melanoma) and skin cancer around eyelids and eyes that people seldom wear sunscreen.
Treating these cancers may sometimes require surgical removal of the entire eyeball.
What kind of sunglasses should I wear?
All sunglasses sold in Australia must meet the Australian/New Zealand sunglasses and fashion glasses standard, which classifies each pair of glasses with numbers 0 to 4.
Class 0 and 1 are not sunglasses, so they are not considered to have the function of preventing ultraviolet rays. Category 2 to 4 can effectively prevent ultraviolet rays, and with the increase of the level, it can reduce the glare of the sun more (but category 4 is forbidden to be worn while driving).
It is very important that the price of sunglasses is not a reference index for its anti-ultraviolet effect. Effective sunglasses should be close to or even wrapped around the whole eyes, so as to minimize the amount of ultraviolet radiation reaching the eyes.
Some contact lenses also contain ultraviolet filtering membranes. However, contact lenses only cover the cornea and cannot prevent pterygium and eye cancer.
When should I wear sunglasses? When the ultraviolet index is 3 or higher, you should always wear sunglasses when you go out during the day, because there is no accurate definition of how safe ultraviolet radiation is for your eyes.
Wearing sunglasses should not be affected by the amount of clouds in the sky, because more than 90% of ultraviolet rays can penetrate clouds. Sand, water and snow also reflect ultraviolet rays. The single-day extreme value of ultraviolet radiation appears from 10 to 2 pm every morning; At this time, people should look for shade to escape.
Children's eyes are particularly sensitive to ultraviolet rays. As long as children accept them, they should be encouraged to wear sunglasses.
Translation: Sun? Revision: Liu Caixing
Original text from: Scientific American Blog
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