What kind of glasses are bifocals?
Bifocals are mainly used in presbyopia correction, providing presbyopic opticians with a clear vision for both near and far use in one pair of glasses. The bifocal lens can be divided into two separate areas, with the upper part of the lens providing clear distance vision and the lower part providing clear near vision. The two regions of the bifocal lens provide different refractive forces, and the difference between these two refractive forces is the reading proximal addition, which compensates for adjustment during presbyopic reading.
GlassesUSA has a wide variety of glasses.
GlassesUSA has a large selection of frames to choose from. Their frames are classified by gender, designer, color, shape, and trend. In addition to sunglasses and sports glasses, there is an area for children's glasses. GlassesUSA has cheap options and expensive frames. To mark the launch of 3D-printed glasses, GlassesUSA is giving consumers the opportunity to design their own frames for an opportunity to win a $300 GlassesUSA gift card.
When should I use blue light glasses?
Most of us spend a few hours a day in front of a screen. Because so many people work on a computer all day, many people wear blue glasses in the office. At the same time, many American high school and college students spend hours a day on their computers and could benefit from blue light glasses.
Orthokeratology lenses are used for myopia control.
The effect of the orthokeratology lens in controlling the increase of myopia in teenagers has been unanimously affirmed by the ophthalmology industry at home and abroad. In February 2006, an authoritative ophthalmological journal published a review of the retarding effect of rigidity breathable orthokeratology lens on the progression of myopia in children. This paper reviews the literature on orthokeratology and myopia in the past 30 years and points out that rigidity breathable orthokeratology can prevent or alleviate the progress of myopia, the mechanism of which is that rigid breathable contact lens can inhibit the progress of myopia by providing clearer retinal image quality. Medium and high concentration of atropine will affect students' near-use vision, while low concentration of atropine has not been used clinically in China, so orthokeratology lens has become one of the known myopia control methods with the best statistical effect. In three to five-year case studies, orthokeratology lenses alleviate a 40 to 60 percent increase in myopia compared with wearing a frame lens or a soft contact lens. Other studies have found that 65 to 70 percent of orthokeratology lens wearers show little or no axial length increase.
What is hard coating on lenses?
Lenses are mainly added in two kinds of film: anti-reflection film and hard film (and some manufacturers produce anti-fogging film and mirror film, but not common). The anti-reflective film is mainly by coating the front surface of the lens with multiple layers of transparent materials with different refractive index and thickness to reduce the excess reflected light on the surface of the lens, by using the principle of light interference. The film can be applied to both glass and resin lenses. The way of hard film plating is usually a soaking process. After many times of soaking and cleaning, soaking in an organic solution containing ultrafine silicon element for a certain time, and then keeping it at a certain temperature for 4-5 hours, the fixed polymerization process of the film has been completed. The surface wear resistance of CR-39 coating can be increased by 2-4 pH, which is similar to the hardness of optical glass lenses.
The origin of aspheric lens
The Visby glasses, unearthed in Gotland, Sweden, are the earliest aspheric lens found. The Vikings in the 11th century used it as a magnifying glass, and some of the best ones were made of silver, making them look like handicrafts. In 1667, Francis Smethwick grinds the first high-quality aspheric lenses and presents them to the Royal Society. That's a telescope with three aspheric elements. In 1956, Elgeet, which originally designed and manufactured optical instruments for the U.S. Navy, produced the world's first mass-produced aspheric lens for photography (Golden Navitar 12mm F1.2) for a 16mm film machine. Today, aspheric lenses are found in everything from tall telescopes to missile guidance systems to camera lenses. In the glasses we wear, the aspheric lens is familiar to consumers.
Best Frames For Heart-Shaped Faces
The heart-shaped face should be one of the favorite faces of Asians. It is characterized by a wide forehead, prominent cheekbones, and narrow and pointed lower jaw. This face shape is not balanced up and down in appearance, and the upper part is larger and more prominent than the lower part. Need to wear sunglasses with a wider bottom, which can increase the width of the lower half of the face. The lower mirror foot position also helps to improve this effect. Don't pick a special big style, normal size will do. Pilot sunglasses with a more angular top and bottom can be used to balance the roundness of the heart-shaped face and chin, increase the sense of facial lines, and visually make the face fuller. Retro black round sunglasses, coupled with a handsome choker, highlight the full street casual style. The recently popular 'inverted triangle sunglasses' are also very suitable for heart-shaped faces. The raised angle of the frame can correct the facial lines and add some angularity to the face. The inverted triangle sunglasses also have a retro temperament, and it feels that there is a mysterious demeanor hidden.