Refractive index of spectacle lens
It is generally believed that the higher the refractive index, the better the spectacle lens. Such spectacle lenses are relatively thin, and of course, the price is a bit expensive. When the refractive index increases, the direction of the light entering the lens will change greatly, the focus will move to the lens, the focal length will be smaller, and the diopter will become larger. In order to keep the diopter unchanged, it is necessary to reduce the curvature of the lens, that is, to reduce the curvature of the mirror surface, so that the thickness of the lens can be reduced. This is why the larger the refractive index, the thinner the lens is. Under the same premise of other things, the larger the refractive index, the thinner the lens, the lighter and more beautiful the lens, and the higher the price, but the larger the refractive index is not the better.
What Are the Disadvantages of Progressive Lenses?
In this section, we will show you some progressive lenses disadvantages.
1. You must learn how to see through the lens. Since there is no visible line in progressive lenses, you may need one or two weeks to learn the correct way to look through the lens.
2. Temporary vision distortions. The lower part of a progressive lens is magnified since it is designed for reading. So, when you look downward when stepping off a curb or walking upstairs, your feet may appear larger through the progressive lens so that it is difficult for you to gauge your step.
3. Progressive lenses are expensive than traditional glasses. So, when you purchasing the progressive lenses, you can compare several different optical stores. In addition, Koalaeye Optical, a professional glasses provider, offers various glasses including cheap progressive lenses, sunglasses, blue light glasses, and so on. Besides, it provides the free shipping service.
How to clean a contact lens case?
Avoid cleaning contact lens cases with running water. Tap water contains a number of chemicals that can be harmful to contact lenses, as well as microorganisms such as bacteria. Please rinse and disinfect with boiling water. Use contact lens solution before cleaning. Let it dry. Make sure the contact case dries naturally before you use it. Stay away from cosmetic bags. It is to avoid that your contact lens case is contaminated by cosmetic bags. Some dust from cosmetic products can easily contaminate contact lens cases, so stay away from cosmetics.
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How to Get Used to Progressive Lenses?
How to adjust to a pair of new glasses? How long does it take to adjust to a new pair of glasses? In general, there are several ways for adjusting to progressive lenses. In this section, we will show you some of them.
- Put on your new progressive glasses in the morning and wear them for at least one hour or two. The next morning, try a few more hours. Develop your tolerance to adjust to them.
- When you walk, look straight ahead, not down at your feet. And, point your nose in the direction you want to look, not just looking left or right with your eyes.
- Don’t switch between your new pair and the old one frequently.
- Make sure your progressive glasses fit properly and don’t slide down your nose.
- When you read, don’t move your eyes or head. Move the page or paper instead.
- Set your computer screen below eye level. You can achieve that by adjusting your desk or chair.
How to stop glasses hurting behind ears?
When adjusting glasses to the optical shop, you can let the staff check if the bending hook is flat. If there is a problem, put it on the polishing machine. The most important thing is that when adjusting the glasses, the height of the glasses temple should be adjusted according to the shape of each person's face, to further increase the comfort of the glasses. Furthermore, if you do not want to go to the optical store, you can make the glasses temple a little loose at home or put a little cotton or paper towel in the ear to prevent friction. You can buy soft eyewear online or at an eyeglass store to prevent ear friction and injury
What Is a Prism in Glasses?
Prism is triangular and made of plastic or glasses for the purpose of dispersing light into a spectrum or changing the direction in which light is reflected.
Prism lenses are special lenses that are prescribed by eye doctors and infused into regular lens prescriptions. The prism glasses do not include contain any focusing power, and therefore cannot any refractive errors. So, one of the most common uses for prism glasses is to correct diplopia or double vision. Double vision means someone sees two separate images of a single object. The prism glasses help to align the two images and correct the problem. The prism glasses can be used to improve binocular vision and reduce double vision, headaches, reading difficulties, and so on.