Where to Buy Long Distance Glasses?
To buy long distance glasses, you can go to the local optical store. Meanwhile, for your convenience, nowadays, you can buy long distance glasses online. Hence, Koalaeye Optical is strongly recommended which provides all kinds of eyeglasses, sunglasses, and frames. You can choose the best suitable one from here. You can also choose a pair of long distance glasses to correct your vision.
What is a drop ball test?
The Drop Ball Test, known as the Basic Impact Test, is an Impact Test administered by the Food and Drug Administration to determine the safety of eyeglasses. Eyeglasses (sunglasses, exercise glasses, near-sightedness glasses, reading glasses, etc.) are a category of medical devices covered by the Food and Drug Administration. When glasses are exported to the United States or put on shelves on Amazon,eBay, and other platforms, they need to be registered by FDA. Besides the product listing, when the product passes the customs, the company may be asked to produce a Certification Statement of Impact Resistance stating that the product meets 21CFR801.410 Drop Ball Test requirements.
What is cellulose acetate?
Cellulose acetate refers to a thermoplastic resin obtained by esterification with acetic acid as a solvent and acetic anhydride as an acetylating agent under the action of a catalyst. It is the first commercially produced and continuously developed fiber among cellulose derivatives. Vegetarian organic acid esters.
The shape of the lens is also important.
Aviator and cat-eye glasses should be avoided, as both will cut off the base of the prescription, resulting in poor reading vision. Instead, they should opt for shorter frames with rounded edges, such as bull horn frames, vintage wingtips, round frames, and oval frames.
How to choose a spectacle frame
First of all, we must clarify what are the specific materials of the spectacle frames on the market. At present, the more commonly used glasses frame materials are sheet material, aluminum-magnesium alloy, natural wood, and bamboo materials. Of course, there are other materials such as titanium, TR90, and ULTEM.
Secondly, we have to make it clear that the texture brought by each different material is different, and each has its own advantages. For example, plastic glasses frames are made of sheet materials, which are characterized by easy processing and relatively lightweight. They are generally not easy to deform at room temperature. And the spectacle frame made of metal material is relatively strong, light, and beautiful. Therefore, to learn the advantages and disadvantages of each type of spectacle frame, we can meet our different needs according to each different material.
Contact Lens Material - Hydrogels
The raw material of the hydrogel is called HEMA. HEMA is hydrophilic and has a water content of 38% by itself. By cross-linking with other polymers, the water content can be up to 80%. The world's first soft cloaking material (OttoWichterle, 1961) was made from HEMA, called PHEMA. Nowadays, most conventional hydrogels are made up of the copolymer of PHEMA and other monomers.
The principle of the anti-fog lens
Ordinary lens materials and water are wet, so water vapor is easy to fog up on the top. If this wetting relationship can be broken, the water vapor can be prevented from fogging up on the surface of the lens. The anti-fogging film is a kind of film which can prevent or avoid water mist agglutination effectively. It is divided into organic film and inorganic film. The inorganic film is mostly used for building, car window glass fogging prevention. For lens anti-fogging, the organic film is more used. The method is to wipe, spray (with an anti-fogging agent, and so on).
