The refractive index of the lens is related to the thickness of the lens.
The main factors that determine if a pair of finished glasses are beautiful, portable, and comfortable depending on the thickness and thinness of the processed lenses. Depending on the material, the index of refraction is different. If you just look at the refractive index, the higher the refractive index at the same degree, the thinner the lens will be. The thinner the lens will be, and the more beautiful the lens will be. However, the higher the refractive index, it is not the better. You can choose the refractive index lens suitable for yourself. But the refractive index is not the only factor that determines lens thickness. Think about the distance between your eyes and the size of the frames you choose, which can affect the thickness of the lenses you match. The larger the pupil distance, the smaller the frame, and the thinner the lens.
What are bifocals?
A bifocal lens is a lens with two focal points. Because of the imaging principle of the lens, even half of the lens can still present a complete image, and the two images do not interfere with each other. In the past, both short-sighted glasses and presbyopia glasses were called single-focal lenses, which had only one focus. Later it developed to the bifocal lens, and the same lens is divided into upper and lower two parts. The upper part of that lens is used when seeing far, and you look down when seeing close objects, just the reading distance, naturally used the second half.
The price of prescription glasses
You need a current (unexpired) prescription to order glasses online. You will enter your prescription and select the available lens options during checkout. Prescription glasses start at about $40. Single vision lenses are free when you buy the frames, and progressive wireless lenses typically cost an extra $80 or so. Other lens options include clear lenses with no extra charge, basic tone lenses (for sun protection) with the price of $40,polarized-tone lenses (for protection and glare reduction)with the price of $50, and transition lenses (for indoor and outdoor use) with the price from $65.
Blue light in natural light
Blue light is not the unique light emitted by electronic products, but the visible light that exists in natural light, usually with a wavelength of about 400-500nm. The blue light in the entire waveband can be subdivided into two parts. One part will cause optical damage to the retina of the eye and accelerate the oxidative senescence of cells in the macular area of the retina. Usually, the wavelength of this part of blue light is between 415-450nm, and its damage to the eyes is gradually accumulated and formed. There is also a part of blue light that is beneficial to our human body, that is, blue light with a wavelength of about 480nm. It can adjust biological rhythms and is helpful for sleep, mood, and memory. In addition, experiments have confirmed that daily outdoor activities in the sun can effectively prevent the occurrence of myopia, and short-wavelength blue light may play an important role.
Points To Note When Choosing Frames
Choose a frame with lightweight, good elasticity, and stable structure. The lens frame with poor quality tends to deform in use, which affects the optical properties of the glasses. Pay attention to whether the two sides of the frame are symmetrical and whether it is fixed and safe enough. Pay attention to whether there are scratches on the surface of the frame. Just put on the glasses to feel if it is very tight or very loose, and they must be tight to reach the saturation condition. Pay attention to distinguish the advantages and disadvantages of the coating. The better coating frame has a uniform color, smooth surface, and clear identification. After using the frame with poor coating quality, the frame will soon rust and fall off, affecting the life of the frame, and even causing skin discomfort or allergy.
How to Clean Glasses
To clean glasses by yourself, you need to be careful and use the correct way to avoid some damage to the glasses such as scratches, etc. So, follow the below steps to clean glasses lens.
1. Before cleaning the eyeglasses, you need to wash and dry your hands first. You can use the soap to wash your hands dry them.
2. Rinse your glasses under a gentle stream of tap water. This way will remove dust and other debris and avoid causing scratches on your lenses. But one thing you need to pay attention to. Please do not use hot water since it can destroy some eyeglasses lens coatings.
3. Use a small drop of lotion-free dishwashing liquid to each lens. You can only use lotion-free brands.
4. Then gently rub both sides of the lenses and all parts of the frame. Make sure to clean every part of the eyeglasses.
5. Rinse both sides of the lenses and the frame. Make sure to remove all traces of the soap. Otherwise, it will cause the lenses to be smeared when you dry them.
6. Shake youreyeglasses to get rid of the water on your lenses gently and inspect the glasses carefully to make sure they are clean.
7. Then dry the lenses and frame with a clean and lint-free towel. Make sure the towel is clean, or the dirt or debris on the towel will smear and scratch your glasses.
After all steps are finished, you also need to check your glasses again and check whether they are clean.
As for how to clean glasses, you can follow the above steps. But when cleaning your glasses, you should be careful enough. When cleaning your glasses, something you can’t do. In the following section, we will list some of them.
Choose the right clear sunglasses for your face shape.
A clear eyeglass frame suits the person of different face shapes according to different shapes. For example, a heart-shaped face suits the clearest eyeglass frame, and a square face suits an elliptical transparent eyeglass frame. A round face suits the clear eyeglass frame with an outline. The long face suits the clear eyeglass frame with some width and so on. There are many kinds of clear frames, like oval, round, square frames, and so on.
When choosing clear frames, be careful to choose one that fits the shape of your face. Oval and the round clear frame are more suitable for heart-shaped faces, square faces, and long faces. People with round faces should avoid large frames, dark frames, and wide edges, and don't wear round or square frames.