Excessive sunlight is harmful for eyes so sunglasses have been especially designed for this purpose. It helps in protecting the eyes as they are the most sensitive area of our body. Tissues of eyes can be easily destroyed by the continuous and overexposure to the sunlight radiations which are visible or non visible in the spectra. Bright sunlight is usually very distracting and annoying but overtime exposure can cause headaches or sore eyes while also may cause permanent damages to the retina, lens or cornea. Temporary damages of overexposure may result into reduction in vision called snow blindness. Permanent effects include cataract eyes or even the loss of night vision. So hence it is proved that the damage is caused by the ultraviolet (UV) rays which is harmful and burns the surface of the cornea.

Basic idea kept in mind while inventing the sunglasses was to help in reducing distracted glares and giving comfortable view and reading in the bright light. Initially, sunglasses had simple tinted glass or plastic which were only helpful in reducing the brightness. So, darker lenses were considered better as they screened out the more light. As soon as we got knowledge about the harmful reaction of ultraviolet rays of sunlight, we knew there is definitely a need of better type of glass to be used in sunglasses for the protection of our eyes.

Technology jumped from the inexpensive models which were made of plastic lens and frames to costly ground glass lenses. Famous brands used this new technology with the custom-made frames; sunglasses were then available in astounding array of styles and costs. Unfortunately, there is only no way to know if the lens really gives a protection from ultraviolet rays by the darkness of the lens.

Raw Materials

Exact definition of sunglasses may be, it consist of two light-filtering lenses plus a frame which hold them in place. Usually lenses are made of colored plastic, like polycarbonate etc. Whereas, glass lens is consider as the high quality branded version of sunglasses. The premier excellence of lens are optically perfect and which don’t distort shapes or lines. For example, camera lenses are made up of distortion free ground and polished optical glass. The scratch resistant glass is known as borosilicate which is made after the tempering it with different chemical treatments.

Metallic oxide pigments and soluble organic dyes are used to the lens material which might absorb or reflect light of certain frequencies of light. But on the other side we have to make sure that these additives should not excessively distort colors. For example bad lens color may cause difficulties in discerning the traffic lights. Gray colored lenses produce least distortions, while amber and brown are equally good. Excessive distortion may caused by the color blue and purple. But additives should be blocking blue light (part of the lower frequency UV rays). For that usually brown or amber are used to screen out that blue light, but which may cause some color distortion. But there are ways to increase the viewing quality by giving the lens various chemical coatings, it will also reduce reflection and control polarized light.

Now, the frames, they are made up of metal or plastic. Metal frames, are usually expensive as they are produced by the mixtures of nickel and other metals like silver or steel. They also have special features like, carved and gimbaled nose pads, sturdy axis with manual locking screws, and stretchy temples. Branded sunglasses usually use the nickel, stainless steel, silver, graphite, and nylon in their cutting edge designs.