Obtaining the correct knowledge of eyeglasses and lenses, which you do not know unexpectedly, will help you to care for your own eyes and eyesight. Please use it as a reference for living a healthy and comfortable visual life.
Vol.11 Story about polarized lenses
We have introduced color lenses and dimming lenses in "Story of Glasses and Lenses Vol.8 , Vol.9 , Vol.10".
This time, we will talk about "polarized lenses".
Some people think of the word "changing lens" in the sense that the color changes, and some people confuse it with the dimming lens of Vol.10. I'll guide you.
1. What is polarized light?
Light emitted from the sun and lighting equipment travels in various directions. This is called unpolarized or unpolarized.
When the light hits fine particles in the air and is confused (confused light), or when it is reflected by glass or the surface of the water and becomes a regular direction, it is called "polarized light".
In other words, when the light hits something, the direction of travel is determined, and the "light is biased".
A laser beam is a typical practical example of polarized light.
Some 3D used in movie theaters and theme parks also use polarization technology.
2. What is a polarized lens?
It is made by sandwiching a special film called a polarizing film between lenses, or a lens with a function to control polarization as a coating on the lens surface.
The products and colors we handle differ depending on the manufacturer and retailer, but we can make them with or without prescription, and the materials used for the lenses are also different.
Some are made of glass, while others are made of polycarbonate.
The light (polarized light) reflected on the glass surface or water surface is controlled by a filter or coating to reduce glare, and there is almost no difference in the effect with any type of polarized lens.
Visible light transmittance and degree of polarization are numerical values that can be compared as differences in the appearance of polarized lenses.
Visible light transmittance is the rate at which light passes, and is expressed as a numerical value from 0 to 100%.
A low transmittance (close to 0%) cuts light, and a high transmittance (close to 100%) allows light to pass through.
In terms of the density of a color lens, the color is darker when the transmittance is close to 0%, and the color is lighter when the transmittance is close to 100%.
The degree of polarization is the ratio of blocking polarized light (reflected light), and is expressed as a numerical value of 0 to 99% like the transmittance, and there is a definition that "a polarized lens with a degree of polarization of 90% or more".
2-2 Polarized lens color
2-1.Accommodative power and presbyopia
Polarized lenses of various colors are available depending on the lens manufacturer and retailer.
As mentioned in the story of color lenses in Vol.8, please see that for the role of color.
2-3 UV protection for polarized lenses
Of course, you can also take measures against ultraviolet rays with polarized lenses. Most polarized lenses are UV-cut, but as mentioned in the story about UV rays in Vol.9, the life of the lens depends on whether it is UV-cut or a UV-cut material.
2-3 Polarized lens life
Polarized lenses have a limited lifespan.
With polarized lenses made with a polarizing filter in between, color unevenness will be seen from the periphery of the lens in about 2 to 3 years, depending on the usage environment and frequency of use.
This is a state in which the part where the polarizing filter and the lens are adhered has peeled off, and the polarizing function has also deteriorated. The main causes are deformation of the lens due to heat and moisture invading the filter part.
The biggest cause of shortening the life of coated type polarized lenses is scratches on the lens surface.
Regardless of the period of use, the coating will peel off from the scratches on the lens surface due to wiping the lens with sand or dust on it, or hitting it against a hard object, and the polarization function will deteriorate. increase.
If you continue to use it with its polarization function deteriorated, it will affect the appearance, so consider replacing it as soon as possible.
However, if you can see far away by correcting your vision with glasses or contact lenses, you will not be able to move the focus on the retina unless you use your accommodation power to see near.
In addition, if the power of glasses or contact lenses is too strong for the eyes, "overcorrection", you will have to use your accommodation power to see things normally, just like people with farsightedness. Because it is in a state, it becomes easy to get tired.
As it is said to be "smartphone presbyopia", even young people can suffer from eye strain due to overuse of accommodative power, deterioration of visual acuity, and even a decrease in work efficiency. We recommend that you consult with an ophthalmologist or optician staff.
3. Accommodative power and spectacle lenses
When it becomes difficult to focus on your hand due to a decline in accommodation power due to aging, single focal lenses called reading glasses and progressive lenses such as near, middle, and near near vision support. See Vol.4, 5, 6, 7.
Regardless of which lens you use, it is important to make it with the appropriate power for the purpose of use. In addition to actually experiencing it at the store, please consult with an ophthalmologist or optician staff about the conditions of use and the distance to the object, etc., and let us know your requests. In order to make better glasses, there is nothing better than having a lot of information. We recommend that you bring your own glasses, as we can improve accuracy if you ask us about any problems with the glasses you are currently using.
Example of distance to target
4. Consider eye health
If you suffer from eye strain due to overuse of accommodative power, it is best to rest without using your eyes.
Since ancient times, it has been said that "when your eyes are tired, it is good to look at distant scenery." It makes a lot of sense because it is When looking into the distance, it's best to relax as much as possible rather than looking at a single point. Sometimes I close my eyes.
It can be said that eye massage and warmth are also effective. At the end of the day, let's take care of the eye muscles that worked hard. Even if you put your hands on your eyes and warm them up during your free time at work, it will be effective.
At our store, staff with specialized knowledge will carefully listen to each customer's situation and propose the best eyeglass frames and lenses. Recently, we have heard many complaints about eyestrain, so please do not hesitate to contact us.