bit of history: how were sunglasses
That direct sunlight harm the health of the eye known by the ancient Egyptians.They used a special painted papyrus, in order to protect the face and eyes from the scorching Egyptian sun.And in the tomb of Tutankhamen was even found a prototype of modern glasses - design, consisting of bronze plates, which connects the two finest saw cut emerald.Still, the first ancestors of modern glasses appeared in ancient China.Lenses for them were glass, which were made of smoky quartz.These glasses are not bad protected from the bright, blinding sun.
Points constantly improved, but there was no mass production.They do haberdasher and zerkalschiki and sold them on the usual market stalls.In XVI points began to make jewelers.They are not used for the production of polished plates of precious stones and pounded.With this lens crumbs became light-absorbing glasses.But these points were affordable only to the wealthy class.
And only in the XX century sunglasses experienced a revol
How to choose the right sunglasses
Selecting points depends not only on your favorite design.We should take into account many factors: the appropriate size and shape corresponding to the anatomy, and even eye color!For example, the lighter your eyes, so they are more sensitive to UV light.And all of the fact that a small amount of pigment particles in the cornea transmits more light in the eye.Therefore, it is desirable to choose a light-eyed glass with a higher degree of protection.How to choose them?
course, you should not rely solely on the label "UV protection".The vast majority of models sold in the street markets and even the mall for a little money do not have UV-absorbing filters.These glasses are in fact not only fulfill their role, but even cause damage to the eyes.This is because the dark glasses limit the amount of light entering the eye, but do not protect from UV rays!Pupil "thinks" it's all right, expands and allows more UV rays to penetrate inside.When choosing glasses also important to pay attention to the fact that the glasses were a good anti-reflective coating.For example, in low light reflection sun's rays penetrate through the dark lenses in the dilated pupil, and can cause burns of the retina.Therefore, glasses with anti-reflective coating contribute to poor eye strain can cause headaches and discomfort.
also a big role in high-quality sunglasses plays color lenses.Of course, the best option is gray-green lenses.Lenses green barely transmits ultraviolet and infrared rays.
Grey lenses allow to perceive color naturally.But the glasses with red, orange and yellow filters increases intraocular pressure, causing spasms ways in which departs eye fluid.
There is photochromic lenses with silver.They are called "Chameleon", as they darken gradually as the light intensity increases.This gradual dimming provides the gentle eye protection.
particular with the color, pay attention to the lens material.They are made of glass and plastic.Any glass lens held ultraviolet radiation, thereby protecting the eyes.But the glasses with glass lenses are unsafe.They can easily break and damage your eyes.Plastic lenses are more durable unlike glass.They are made of acrylic or polycarbonate plastic.Even if the plastic lenses are broken, the shards from them safer than shards of glass lenses.Less plastic lenses - is that the refractive index of the plastic is less than the glass.And plastic less durable than glass and scratched faster.If you leave the choice to the plastic lenses, keep in mind - to protect from the UV radiation can only quality plastic lenses, which are expensive.
When choosing sunglasses, you must also pay attention to the rim.Be sure to evaluate the mobility of nose pads.If they are too rigid, there is strong pressure on the nose, which can lead to fatigue.Temples should not put pressure on the temples, as well as the area behind the ear.Their size must strictly correspond to the distance from the rim to the bulge behind the ear.