Before discussing the relationship between ultraviolet rays and the eyes, do you know why ultraviolet rays are so called?
Light and heat travel to the Earth from the sun, and ultraviolet rays constitute one type of ray involved in this process.
No doubt you will all have seen rainbows that appear when the weather clears up after a rainfall or when you are spraying water on your garden. A rainbow is a phenomenon that results from light from the sun being divided into the 7 prismatic colors of red, orange, yellow, green, blue, indigo and violet when it passes through moisture in the air. These colors are called "visible rays" because of their visibility to the human eye.
However, these are not the only light rays that travel to the Earth from the sun. There are also rays that fall outside the range of "visible rays" that are invisible to the human eye. Two typical examples of these invisible rays are "ultraviolet rays" and "infrared rays."
The reason the term "ultraviolet rays" was coined is simply that, as the term implies,
this kind of light is "beyond (ultra) of the range of violet light."
Light is composed of electron waves called magnetic waves and the colors red, orange, yellow, green, blue, indigo and violet that occur in order of the length of the space (wavelength) occurring between these waves are reflected in the human eye. The 7 prismatic colors of a rainbow are also aligned in this order. These colors represent the "visible rays" mentioned earlier. Colors with wavelengths longer or shorter than these seven are invisible to the human eye.
Ultraviolet rays have a wavelength even shorter than violet, the visible ray with the shortest wavelength of all, and this is why the term "ultraviolet" is used; i.e. beyond (ultra) violet. This is where the term "UV," an acronym for Ultra-Violet comes from, and it can be seen in expressions such as "UV-cut," an ultraviolet ray-blocking function applied to cosmetic products, for example.
Rays with wavelengths longer and, therefore, beyond the red wavelength are called "infrared rays."
There are three different types of ultraviolet ray, classified beginning with the shortest wavelength into "UV-C," "UV-B" and "UV-A,"
Moreover, ultraviolet rays play a significant role in a condition called "pterygium." Pterygium is a condition that produces an extreme propagation of the tissue that forms the whites of the eyes with result that this tissue begins to obscure the irises. Pterygium can be cured through surgery, post-surgical recidivism is common. It is known that the rate of occurrence of conditions such as pterygium and cataracts is even greater in regions with high concentrations of ultraviolet rays.
Furthermore, ultraviolet rays entering the eyes also have serious effects on the skin. Even though the skin may not be exposed, the eyes sense the penetration of ultraviolet rays and subsequently send signals throughout the body. This results in the formation of melanin pigments to resist the ultraviolet rays, producing a state identical to that which occurs when the skin itself is directly exposed.
This gives us an idea of the extent of the effects of ultraviolet rays on the health of both the eyes and the body.
Incidentally, although ultraviolet rays are at their peak in early summer, their effects can also be felt in other seasons, as shown in the graph below. We need to be sure to take measures to protect ourselves from ultraviolet rays not only during the summer, but throughout the entire year.
The following are effective measures to protect the eyes from ultraviolet rays:
UV-cut spectacles or sunglasses protect our eyes not only from the glare of bright sunlight, but also from ultraviolet rays invisible to the human eye, and are, therefore, very useful during seasons when the level of ultraviolet rays is high. However, care should be taken when purchasing sunglasses since not all products have UV-cut functions.
Items such as hats and parasols are effective when used together with UV-cut spectacles and sunglasses since they help to prevent ultraviolet rays penetrating the gap between the face and the lenses, an effect that cannot be achieved by UV-cut spectacles or sunglasses alone. Use of items such as hats and parasols together with UV-cut spectacles or sunglass, therefore, increases the UV-cut effect. Incidentally, remember that the brim of the hat should preferably be at least 7 centimeters wide.
Let's take a look at the comparative effectiveness of various means of protection against ultraviolet rays:
We can see at glance which is the most effective method of protection against ultraviolet rays.
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[Product Information] New spectacle lens for everyday use to protect the eyes from UV rays and glare
We will be exposed to greater amounts of sunlight in places like beaches or in the mountains than in our ordinary daily lives. At the beach, the eyes are exposed not only to direct sunlight, but also to light reflected from the surface of the sea or the sand. The amount of ultraviolet rays increases in proportion to increases in sunlight.
When mountain climbing, you should also bear in mind that the amount of ultraviolet rays increases the higher you climb.
Although the air absorbs ultraviolet rays from the sun, air becomes thinner at higher altitudes in the mountains, for example. In the same way, the higher the altitude, the lower the atmospheric pressure. For this reason, the amount of ultraviolet rays is greater at the top of a mountain than at the base.
Sunglasses are essential for driving in environments with exposure to strong sunlight. To protect our field of vision from midday sunlight or bright glare from the setting sun so that we can drive safely, sunglasses are an essential consideration. In addition, since it is not possible to select shaded spots when driving, ultraviolet rays are also a concern. When driving, we are apparently exposed to greater amounts of ultraviolet rays than we imagine due to exposure not only to direct sunlight, but also to light reflected from the road, for example.
Lens colors should be selected according to the purpose for which sunglasses will be used.
For example, brown tints are suitable for golf while blue or gray tints are preferable for swimming at the beach.
Naturally, we all have our own color preferences and colors that suit us.
We hope the characteristics of various colors described above will help you find the ideal color for you.