A bit of history: how sunglasses appeared
Even the ancient Egyptians knew that direct sunlight harmed the health of the eyes. They used a special dyed papyrus to protect the face and eyes from the scorching Egyptian sun. And in the tomb of Pharaoh Tutankhamun even a prototype of modern glasses was found - a design consisting of bronze plates that connected the two finest pieces of the emerald. But still the first progenitors of modern glasses appeared in ancient China. Lenses for them were glass, which were made of smoked quartz. These glasses are well protected from the bright, blinding sun.
The glasses were constantly improved, but there was no mass production. They were made by haberdasheries and mirrors, and they were sold on usual market trays. In the XVI glasses began to make jewelers. They used to produce non-polished plates of precious stones, and crushed. With the help of this crumb, the lenses of the glasses became light-absorbing. But such points were affordable only for the wealthy class.
And only in the XX century, sunglasses survived a real revolution. Even at the beginning of the century glasses for protecting the eyes from the sun's rays were a rare piece of goods, the privilege of rich people. For their manufacture, tortoiseshell, horn, precious metals and stones were used. In the 1920s, there was just a boom in the popularity of this accessory, to which Coco Chanel herself had a hand. But even so, sunglasses became a consumer goods only in the fifties of the last century.
How to choose the right sunglasses
The choice of points depends not only on the design you like. Many factors must be taken into account: both the appropriate size, and the shape corresponding to anatomical features, and even the color of the eyes! So, for example, the lighter your eyes, the more sensitive they are to the ultraviolet. And all due to the fact that a small amount of pigment particles in the cornea allows more light into the eyes. Therefore, it is desirable for light-eyed to choose glasses with a greater degree of protection. How to choose them?
Of course, do not rely only on the label "UV Protection". The vast majority of models sold in the street, the market and even the shopping center for small money do not have UV absorbing filters. Such glasses in fact not only do not fulfill their role, but even lead to eye damage. This is because dark glasses limit the amount of light that gets into the eyes, but does not protect against ultraviolet rays! The pupil "thinks" that everything is in order, expands and allows more ultraviolet rays to penetrate inside. When choosing glasses, it is also important to pay attention to the fact that the glasses were with a good anti-reflective coating. So, with poor light reflection, the sun's rays penetrate through the dark lenses into the dilated pupil, and can cause a retinal burn. Therefore glasses with a bad anti-reflective coating contribute to eye strain, can lead to headaches and discomfort.
Also, the color of lenses plays a big role in quality sunglasses. Of course, the best option is the gray-green color of the lenses. Lenses of green color almost do not pass ultraviolet and infrared rays.
Gray lenses allow you to perceive colors naturally. But glasses with red, orange and yellow light filters increase intraocular pressure, cause spasms of the pathways through which the eye fluid leaves.
There are also photochromic lenses with silver. They are also called "chameleons", because they darken gradually, as the brightness of light increases. This gradual darkening provides the most sparing protection to the eyes.
Having decided on the color, pay attention to the lens material. They are glass and plastic. Any glass lens retains ultraviolet radiation, thereby protecting the eyes. But glasses with glass lenses are unsafe. They can easily break and damage your eyes. Plastic lenses are more durable than glass ones. They are made of acrylic or polycarbonate plastic. Even if plastic lenses are broken, then fragments from them are safer than fragments of glass lenses. The downside of plastic lenses is that the refractive index of plastic is less than that of glass. And also the plastic is less durable than glass and scraped faster. If you have left your choice on plastic lenses, then please note that only high-quality plastic lenses that are not expensive can protect against ultraviolet radiation.
When choosing sunglasses, you must also pay attention to the frame. Be sure to assess the mobility of the nose pads. If they are too rigid, then there is a strong pressure on the bridge of the nose, which can lead to rapid fatigue. The temples should not exert pressure on the whiskey, nor on the area behind the ear. Their size should strictly correspond to the distance from the rim to the bulge behind the ear.