Contact Lens Material - PHEMA material
It is the earliest material used in the production of contact lens hydrophilic material. The main advantage is water absorption, with a water content of about 38%. The material is soft, but its disadvantage is only partial oxygen permeability.
What factors make you receive glasses on the same day?
Are your lenses anti-glare or anti-scratch? This may extend the time it takes you to buy glasses. Is your prescription complicated? If so, it could mean your lenses take longer to make. Your favorite frames that you tried out at the store are just for display, so you have to order frames for your glasses. If that particular frame style is in small quantities at the factory, your delivery may be delayed. Some optometrist offices and eyewear retailers have in-house optics LABS. These LABS can make some eyeglass lenses in an hour or so. But the power and design of the other lenses needed to be manufactured by an external optics lab, which took more time.
Anti Blue Light Glasses For Kids - Felix Gray Nash
This square frame is stylish and comfortable, and children will love this popular color. In addition to filtering out blue light, the glasses eliminate glare. There are four different colors.
What Do the Numbers on Glasses Mean?
The first number on glasses frames is the eye size. It is the horizontal width of the lenses. In general, the number of eye sizes varies from 40 mm to 62 mm in most of the spectacle frames.
The second number is the bridge size. It is the distance between the lenses. Also, it is the bridge that rests upon your nose. Mostly, the size of the bridge on glasses frames would be from 14 mm to 24 mm.
The third number is the temple length. It is the length of the stems of the frame that rests upon your ears. It can be measured from hinge to the end tip of the temple. In general, the temple length in most cases is from 120 mm to 150 mm. The bridge and temple help the frame to comfortably fit on the face.
Meanwhile, if there are no numbers on glasses frames, do not worry. You can always measure your eyeglasses frame with a millimeter ruler. Sometimes, the tiny numbers are worn off or sometimes they are printed too small that you might have to use the magnifying glasses. If you have known the glasses numbers meaning, you can choose to measure them by yourself.
At the same time, to fit the glasses better, you can also choose to measure your face for glasses frames. After knowing the suitable size of glasses, you can choose to buy a pair of glasses online. Thus, Koalaeye Optical is recommended. It is an online glasses store and provides all kinds of glasses, sunglasses, and frames. What’s more, these glasses are stylish and cheap.
What Are Progressive Glasses?
Trifocal glasses and no-line progressive lenses are multi-focal glasses, meaning that their lenses offer multiple correction fields. Whether you have been wearing multi-focal glasses for a while, or you have just begun to look at options for correcting vision after 40 years old, you may have heard the terms trifocal or progressive glasses.
Progressive lenses offer a smooth transition from distance vision through intermediate vision to near vision, and they supply all the in-between corrections. Progressive lenses have three different viewing zones, as trifocal glasses do, and they have progressive powers of corrections, easing eye strain and providing the most natural vision correction.
Why do spectacle lenses fog up?
The fog on the surface of the lens is essentially related to the saturation pressure and water vapor liquefaction. The air is full of water molecules, which are constantly doing irregular movements. When there is no temperature difference, water molecules keep hitting the surface of the lens and will keep bouncing off. The lower the temperature, the slower the speed of movement. Therefore, when water molecules hit the cold lens from the hot air, on the one hand, they move too slowly to fly out in time. On the other hand, because of the relatively low temperature of the lens itself and its vicinity, the water vapor will liquefy. As a result, more and more water will accumulate on the lens and form small droplets, eventually forming a foggy layer. As the lens heats up, the mist evaporates back into the air, and the fog disappears.
Aspheric lenses are different from spherical lenses.
Spherical lenses: The higher the strength of spherical lenses, the worse the visual experience, because the spherical lenses do not eliminate aberrations. Aspheric lens: it can greatly reduce the deformation of things and make people see more clearly and vividly. Besides, the eyes are not easy to get tired and the appearance is beautiful. It reduces the aberration of the lens and ensures a clearer field of vision.
When the parameters of the lens are normal, the optical center of the myopic lens is the clearest, and the peripheral part of the lens will be slightly deformed. So now the lens is designed with an aspheric surface. Under normal circumstances, the mainstream aspheric lens in the market has a reduced edge design, which is about 5 to degrees lower. The opposite edge of a spherical lens is higher.
