It is common knowledge by now that UV rays from the sun cause a lot of damage to the eye. UV rays are located above the violet portion of the visible light spectrum and its main source is sunlight. There are three main categories of UV, that is, UVA, UVB, and UVC. UVA has a longer wavelength, which allows it to pass through normal glass easily. The information below is worth knowing about sunglasses lens types.
It is an issue of dispute among scientists whether UVA rays are harmful to the eyes. On the contrary, UVB pose a very big danger to eyes because they are capable of causing harm. It is vital put on sunglasses and sunscreen because of the harm UVB causes. UVB rays cannot pass through glass or sunscreen. Lastly, UVC are not available on the surface of the earth because they are blocked by the atmosphere.
As such, it is important to wear sunglasses as a preventive measure against damage that UVB causes. Besides serving as a preventive measure, sunglasses also act as a corrective measure for various eye defects. For instance, people who have myopia or long-sightedness need glasses to be able to see better at close and long range respectively. In order for these glasses to work effectively, they need to have lenses.
There are different types of lenses which give different effect when a person wears them. These types of sunglass lens include progressive, polycarbonate, polarized, photochromic, Hi-index, trifocal and bifocal. A complex front surface is used to make aspheric lenses. This surface gradually changes its curvature from the center towards the edge. These lenses are meant for correcting minor vision distortions. Due to their light weight and thinness, they are suitable for carrying and wearing.
The correction of far-sightedness as well as short-sightedness is done by bifocal lenses. The lens located in the lower part is meant for correcting short-sightedness while that in the upper part of the glass are for improving long-sightedness. Their prescription is mostly for the elderly people because vision develops defects as one ages. Trifocal lenses incorporate into bifocal lenses the ability to see objects that are located only a couple of feet away.
Photochromic lenses are designed in a way that they darken when they are hit by sunlight. This feature is very convenient for most people that would otherwise have to carry multiple sunglasses for different conditions. These lenses are available in all materials and lens materials. For instance, it is possible to find high-index, bifocal, and trifocal lenses that are photochromic. They are a popular choice for people of all ages.
Polarized lenses are designed to reduce the glare that comes from surfaces such as water surfaces, glass, and snow. This makes images to appear clearer and sharper. One can get them in both prescription and non-prescription sunglasses. They can be worn indoors by people who are sensitive to light. Post-cataract surgery patients make very good candidates for glasses with polarized lenses.
Another very common type of lens is the polycarbonate variety. This variety is suitable for people who maintain active lifestyles. For instance, the playful nature of children makes these products very suitable for them. Many parents buy their kids sunglasses with polycarbonate lenses because they are impact-resistant and resilient.
It is an issue of dispute among scientists whether UVA rays are harmful to the eyes. On the contrary, UVB pose a very big danger to eyes because they are capable of causing harm. It is vital put on sunglasses and sunscreen because of the harm UVB causes. UVB rays cannot pass through glass or sunscreen. Lastly, UVC are not available on the surface of the earth because they are blocked by the atmosphere.
As such, it is important to wear sunglasses as a preventive measure against damage that UVB causes. Besides serving as a preventive measure, sunglasses also act as a corrective measure for various eye defects. For instance, people who have myopia or long-sightedness need glasses to be able to see better at close and long range respectively. In order for these glasses to work effectively, they need to have lenses.
There are different types of lenses which give different effect when a person wears them. These types of sunglass lens include progressive, polycarbonate, polarized, photochromic, Hi-index, trifocal and bifocal. A complex front surface is used to make aspheric lenses. This surface gradually changes its curvature from the center towards the edge. These lenses are meant for correcting minor vision distortions. Due to their light weight and thinness, they are suitable for carrying and wearing.
The correction of far-sightedness as well as short-sightedness is done by bifocal lenses. The lens located in the lower part is meant for correcting short-sightedness while that in the upper part of the glass are for improving long-sightedness. Their prescription is mostly for the elderly people because vision develops defects as one ages. Trifocal lenses incorporate into bifocal lenses the ability to see objects that are located only a couple of feet away.
Photochromic lenses are designed in a way that they darken when they are hit by sunlight. This feature is very convenient for most people that would otherwise have to carry multiple sunglasses for different conditions. These lenses are available in all materials and lens materials. For instance, it is possible to find high-index, bifocal, and trifocal lenses that are photochromic. They are a popular choice for people of all ages.
Polarized lenses are designed to reduce the glare that comes from surfaces such as water surfaces, glass, and snow. This makes images to appear clearer and sharper. One can get them in both prescription and non-prescription sunglasses. They can be worn indoors by people who are sensitive to light. Post-cataract surgery patients make very good candidates for glasses with polarized lenses.
Another very common type of lens is the polycarbonate variety. This variety is suitable for people who maintain active lifestyles. For instance, the playful nature of children makes these products very suitable for them. Many parents buy their kids sunglasses with polycarbonate lenses because they are impact-resistant and resilient.
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