Apply sunscreen, wear sun-protective clothing, and that’s it? Protect your eyes from the sun, too!

It's almost the beginning of autumn, but we're still exposed to the sun! Every summer and even early autumn, there are many discussions about sun protection: which sunscreen is the most effective, which sun-protective clothing is both good-looking and provides sun protection. Facing the scorching sun, do you think that applying sunscreen and wearing sun-protective clothing will be enough? Protect your eyes from the sun, too!

01 Why do you need to protect your eyes from the sun?

According to wavelength, ultraviolet rays in sunlight can be divided into three categories:

Short-wave ultraviolet rays (UVC, wavelength 100~280nm) will be absorbed by the ozone layer and cannot reach the surface;

Medium-wave ultraviolet rays (UVB, wavelength 280~315nm) can reach the surface of the earth, are easily blocked by glass, and have strong biological effects;

Long-wave ultraviolet rays (VUA, wavelength 315~400nm) have weaker biological effects, but have extremely strong penetrating ability.

When sunlight hits the eye, it first hits the cornea , then the lens , and finally the retina . The first two are like protective shields for the eye, on the one hand absorbing ultraviolet rays to prevent retinal problems; on the other hand allowing visible light waves (such as blue light waves) to pass through to form normal vision.

Figure 1: Schematic diagram of sunlight shining into the eyes (Source: Evidence for the Role of Blue Light in the Development of Uveal Melanoma)

Of course, this kind of protection is not a panacea. Take the lens for example. If the eye is compared to a camera , the lens is equivalent to the lens , which must have good transparency. In a healthy lens, the proteins are arranged in an orderly manner and have excellent transparency. However, long-term and high-dose exposure to ultraviolet rays, especially medium-wave ultraviolet rays , can change the structure of proteins, leading to protein aggregation and the formation of amyloid deposits . The lens becomes cloudy and the transparency is seriously reduced, which is what we often call "cataracts."

In addition, long-term exposure to ultraviolet rays may also cause eye diseases such as pterygium and macular degeneration .

02 What are the dangers of these diseases?

All of the above diseases can affect vision. Among them, cataracts have the greatest impact on vision. When the lens is significantly cloudy, the patient may not be able to see anything.

Figure 2: Major risk factors for cataracts (Image source: self-made by the author)

In traditional concepts, people regard cataracts as "exclusive" to the elderly. However, the "Research Report on the Current Status of Cataract Cognition and Diagnosis and Treatment in China" shows that in recent years, cataracts have tended to be younger, with patients under 40 years old accounting for 4.55% of the total number of patients. From this perspective, regardless of age, you should pay attention to eye sun protection .

03How to choose and use sunglasses?

So, how do you reduce the impact of UV rays on your eyes? The answer is simple: wear sunglasses correctly.

There are many types of sunglasses on the market. When choosing, you should pay attention to three aspects.

One is the diopter . People who do not need vision correction can choose plain glasses, otherwise they should choose myopia glasses or hyperopia glasses.

The second is the usage scenario . According to national standards, sunglasses are divided into five categories. Among them, category 2 and 3 sunglasses are suitable for use on sunny days in summer, and category 4 is a special sunglasses that cannot be used for walking or driving.

Figure 3: Scope of application of different sunglasses (Image source: GB 39552.1-2020 Sunglasses and sun lenses Part 1: General requirements)

The third is special needs . For example, if you go to the beach, you can choose light blue lenses. However, light blue will interfere with the recognition of traffic lights and should not be worn when driving or crossing the road. Brown lenses can improve contrast and clarity to a certain extent, and are especially suitable for middle-aged and elderly people with poor eyesight.

Once you have decided on the general direction based on your own situation, you can consider purchasing.

In terms of style, try to choose the type that fits your face closely and has wide lenses and frames . This type of sunglasses may not be beautiful enough, but it can provide the greatest protection for your eyes.

Before paying, be sure to ask for receipts, instructions, and product labels . Some people like to shop overseas, and sunglasses are a little special. The standards and labels of different countries are not consistent. When buying foreign products, be careful to identify them.

In terms of wearing, it is best to check the weather forecast before going out, avoid times when ultraviolet rays are strong, and use other sun protection measures when necessary, such as sun hats and parasols . After entering indoor and shady environments, sunglasses should be taken off in time. For children, they should pay special attention to the wearing time , otherwise it may affect their eyesight.

After use, they should be properly stored . According to the instructions, wipe off the dust and put it in a dark place . Some sunglasses are made of natural organic materials and need regular maintenance.

Of course, no matter how careful you are, sunglasses will eventually break. There is currently no accurate way to determine the lifespan of sunglasses, and since each person's usage is different, you can also judge for yourself when to replace them, for example, whether the lenses are scratched or the frames are discolored .

Conclusion

People often say that eyes are the windows to the soul. This window is both important and fragile. Fortunately, it is not difficult to protect it. Here is a reminder for everyone: if you experience eye discomfort, you must go to a regular hospital for diagnosis and treatment as soon as possible.

Author: Zhao Yanchang, member of China Science Writers Association

Reviewer: Peng Qinghua, Professor of Hunan University of Traditional Chinese Medicine, Director of the National Center for TCM Treatment of Fundus Diseases, Director of the Ophthalmology Research Laboratory

Li Nannan , member of the China Science Writers Association, expert on popular science in China

Produced by: Science Popularization China