Operation and Requirements of Drop Ball Test
The ball, which is 0.625 inches in diameter and weighs 0.56 ounces (16 grams), falls from 50 inches (127 centimeters) and hits the center of the lens. The geometrical center of the lens should be struck by the ball within a circle 5/8 inches in diameter. If the lens does not break, it is called a safety lens. There can't be anything that restricts the ball from falling. It cracks across the entire thickness, containing laminated layers (if any), and divides into two or more separate sections across the entire diameter.
Does it take time to adjust to progressive lenses?
How long should it take to get used to progressive lenses? I have never worn glasses before.Progressive lenses were developed to allow easy switching between near and far views. Progressive glasses are divided into four parts. The upper part is the far-light region. The lower part is the near-light region, and the middle part is a variable light region. From top to bottom, if the hyperopia film is gradually increased and the myopia film is gradually decreased. The middle variable area is on both sides of the astigmatism area. Because of the prism effect, when you see things, through this area, the object will be blurred, and the eyes will feel uncomfortable. If the height of the frame itself is very small, the transition zone of progressive multi-focus is very narrow, and the eyes may not adapt to the sunglasses. The current design of progressive lenses is still not mature. Imported brands are relatively stable but expensive, and domestic brands are not mature in design. For various reasons, progressive glasses may be difficult to adapt to wearing.
Why do blue light glasses turn yellow?
The glasses are used for a long time. Blue lenses are usually light yellow. If the yellow is too deep, the resin lenses will oxidize and become yellow due to the long-wearing time. The lenses need to be replaced in time. Yellowing of the lens is related to the excessive secretion of facial grease, which leads to yellowing of the lens. The most direct way is to replace the lens glass.
What Are Non-Prescription Glasses?
Nowadays, many people wear glasses for a variety of reasons and not just for vision problems. In fact, many people wear non-prescription glasses as a fashion statement. This trendy accessory can make you more fashionable.
What are non-prescription glasses? It is important to note that the non-prescription glasses have no corrective power, while non-prescription reading glasses offer some level of magnification, enlarging what you see up-close.
If you don’t have a vision problem, wearing Plano glasses shouldn’t be a problem since they will neither damage your eyes nor cause structural issues. Some non-prescription specs, such as the type that blocks damaging blue light, can actually be beneficial to your eye health.
What Are the Benefits of Non-Prescription Glasses?
In this part, we will show you the benefits of non-prescription glasses and show you what you need to know before buying the non-prescription glasses.
Protection: the non-prescription glasses would provide protection for your eyes from dust, direct sunlight, and computer radiation. In addition, these glasses would have to be enhanced with special coatings.
Fashion: Wearing non-prescription glasses enables you to look more fashionable. The best part is that you can select a pair of non-prescription glasses that have the features you prefer. Besides, many frames are made from high-quality materials that make them durable. They are comfortable and lightweight, which everyone can appreciate. Non-prescription glasses are also available in a variety of sizes, shapes, colors and styles so there will always be something that matches your needs and even your personality.
The benefits of bifocal glasses
People with myopia often need to wear bifocal glasses after the appearance of presbyopia. The upper and lower parts of the lens have different diopters. The upper part is used to see distant objects, and the lower part is used to read and do close work. In addition to presbyopia, some people who work long hours in close quarters need bifocals to reduce eye strain. Studies have shown that long-term nearsightedness is the main cause of myopia. According to the adjustment principle of the eyeball and the height of the patient diopter, a reasonable measure is to wear myopia glasses with full correction when seeing the blackboard in class. When reading and writing. they should take off glasses or wear low myopia glasses. But the practice of continuously removing and putting on or changing glasses is clearly unrealistic. Bifocal glasses will solve this problem.
Choose clear glasses for kids to keep safe.
Safety is very important no matter in what aspect, glasses are no exception. Especially for children, they are more active. The lens is best made of PC, and the frame is best made of materials with high toughness, such as TR90. Service fixed number of years of this kind of picture frame is long.
The nose pad
When you're shopping for a driver's glasses, you can't ignore a nose pad. Choose one that is soft and elastic. This way, it won't make your noses feel depressed or uncomfortable.