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.
How to Choose Reading Glasses?
In this section, we will show you some tips for choosing reading glasses.
Find the right power. When choosing reading glasses, finding the right power would be the most important thing. All reading glasses will have signs or stickers indicating their power. In most cases, they will range from +1 to +4 diopter, in increments of +0.25. So, when choosing reading glasses, try the lowest power first.
Test-drive the glasses. If you have brought reading material with you, try reading it at a comfortable length. If you hold the material too far out to be able to read it, you should increase the power. Keep testing the differences powers until can read clearly at the distance that’s more comfortable for you.
Choose big frames the first time. When choosing reading glasses, you can choose the big frames for the first time. You may need larger glasses frames or lenses to really get the sweet spot of where the prescription is.
And if you have never worn glasses for eye conditions such as nearsightedness, farsightedness or astigmatism, it is likely you will be able to see well with non-prescription reading glasses. So, you can buy these non-prescription reading glasses.
Ray-Ban's clear glasses are of high quality.
As a high-end glasses brand, Ray-Ban leads the youth fashion, frame technology, and style design breakthroughs and innovations. In the shape of the design, the Ray-ban myopia glasses use ergonomic principles and are very consistent with the considerate surface type. They are safe, natural, and comfortable to wear. In the design of the frame, the use of double screws, so that the lens fixed is very stable. And the weak arm end design can be adjusted according to the profile of the face, easy to wear, very bright, and shiny in the vividness of color.
How to clean the lenses?
When wiping lenses (especially the rimless glasses of resin lens), you must use a special wipe lens or soft handkerchief or paper. When you wipe the lens, you can only wipe it in one direction, not in circles, and don't touch the lens with your fingers. When the lens is stained with dust and sand, it should be washed with water before wiping, otherwise, the lens is likely to be abraded, and the operation should be gentle. At ordinary times, when cleaning, do not exert too much force, pay attention to the grasp of strength. When wiping the lens, it is best to take the side frame with one hand, and the other hand takes the glasses cloth to wipe gently. In order to prevent the lens film layer falls off, do not use alkaline detergent to wipe the lens. Therefore, when bathing or playing at the seaside, glasses should be properly kept to avoid water vapor or seawater caused by corrosion of glasses.
Trifocal vs Progressive Lenses: Which Are Better?
Each type of glasses has advantages and disadvantages. Progressive glasses offer the wearer a youthful-looking eyewear option, and they can be customized for specific use. Trifocal glasses are not customizable like progressive, but instead, come in a few standard configurations. Trifocal glasses offer a wider intermediate viewing area than progressive lenses do. Hence, trifocal glasses could be more comfortable for computer use.
In addition, trifocal glasses are cheap than progressive lenses. So, they tend to be more affordable.
What’s more, progressive may be used in prescription sunglasses or in photochromic glasses. Trifocal lenses are mostly used in sunglasses or light adaptive glasses, but these may require a special order.
So, from the above information, you have learned some basic information about trifocal lenses and progressive lenses. As for trifocal vs progressive lenses, you may also have gotten some answers.
Therefore, if you want to buy a pair of trifocal glasses or progressive glasses, you can try Koalaeye Optical. It is an online glasses store, providing all kinds of glasses, sunglasses, and frames. Besides, these glasses are stylish and come at a cheap price. With your great convenience, the package will be mailed for you for free.
Have a try and confirm the front and side of the glasses.
Confirmation data: pupil height, flat frame surface, size of frame surface, the harmony of nose arc, the contact area of nose support, size of temple bend. Finally, remember a big principle: You should have no sense of pressure, and in a small range of motion, the frame does not shift. Good glasses should be perfectly integrated with the face so that people can not feel the existence of glasses. Good design is invisible. The lens above 800 degrees will be slightly heavy, so it is not recommended to choose the elastic temple and smooth metal temple. The temple is too slender, and at the same time is all metal, easy to slide frequently.
Testing of aspheric lens
The optical axis of the optical center just overlaps with the visual axis of the eye, which is the most ideal state. Because the light from the edge cannot form a focus on the optical axis, when the optical axis does not overlap with the visual axis (the difference is greater than 2mm), such unclear and scattered imaging results will occur. When choosing frames and aspheric lenses, you need to ensure that they fit correctly, to achieve the best visual and decorative effects. Simply put, due to the special design of the lens, we found through a calculation that the optical center should move down 1mm higher than the pupil for every 2° increase in front inclination angle. Otherwise, the wrong pupil height will cause the lens to look like astigmatism, and cause discomfort. For glasses with aspheric lenses, there must be an inclination angle after wearing. The specific angle varies from person to person.
