Disadvantages of bifocal glasses
The disadvantage of bifocal glasses is that the different areas are clearly spaced and the appearance is not beautiful. The medium distance is fuzzy, and the adaptation period is needed, there is a prismatic jumping phenomenon. The focal distance between the upper and lower lenses is different, with a clear dividing line. The main disadvantage is that when the line of sight moves from far to near, there will be interference like jumping, and the middle distance object image is blurred. Students can adapt to sitting still in a class by wearing bifocal glasses, but they can only wear glasses when they are in class or studying because of the inconvenience and even danger caused by the interruption of the glasses.
Features of Beta titanium glasses frame
Beta titanium has better strength, fatigue resistance, and environmental corrosion resistance than pure titanium and other titanium alloys. The shape plasticity is very good, which can be made into wire and sheet, more lightweight. They are used to make glasses and can get more shapes and styles. It's the material for a new generation of glasses. Customers with higher requirements for style and weight can completely choose beta-titanium glasses. Because β titanium processing technology is higher than pure titanium, usually only large factories and brands will produce, and the price is higher than pure titanium glasses.
How to Find Reading Glasses Strengths?
Some reading glasses also come with strengths. So, how do you know what strength reading glasses to get and how to find reading glasses strengths? The strength of all reading glasses is measured in dioptre, with units increasing by 0.25 dioptre depending on the power of the lens.
The reading glasses strengths range from +0.75 dioptre to +3.00 dioptre. Both lenses have the same power which is indicated by a permanent marking on the inside of the frame or with a removable sticker on the lens. So, you can find the reading glasses strengths of the glasses.
The important thing you need to notice is that when higher the number, the greater the power of the lenses is when choosing reading glasses. So, glasses with a marking of 1.0 are low power while those marking +3.0 are high powered.
What Are High Index Lenses?
High index lenses are composed of a special plastic that is good at bending light. With this feature, high index lenses can be much thinner than standard lenses while having the same prescriptions.
So, polycarbonate lenses vs high index lenses, what are their differences?
A round face fits on a square frame.
The human face of a round face is shorter. So they had better match the slender frames that take curves slightly to reconcile the whole feeling. Angular and square frames are helpful to modify facial lines (prominent longitudinal lines). This can promote strengths and avoid weaknesses so that your face appears contour.
The characteristics are different.
Cellulose acetate materials have high wear resistance, and hardness and texture are very good. The sunglasses are made of acetate fiber plate with plate cutting and processing. The main materials are plate and plate plus steel sheets. The characteristics of the plate are that they are not heavy. It has a hardness, good gloss, and steel combined to strengthen the firm performance. And they have a beautiful style, not easy to deform and change color, durable. The plated one deduces fashion, easy-to-match clothes, and integrates the thickness of the plate and the texture of the metal, reflecting the personality style.
The chemical name of the CP material is propionic acid fiber, cellulose molecules for the hydroxyl propionic acid in the polymer. It has good weather resistance and low-temperature resistance. The current market of this material is mainly used in glasses, toys, and a variety of shells. It is one of the acrylic resin derivatives. The material is a large sheet and can be dyed in a variety of colors.
39DollarGlasses was developed by ophthalmologists to provide people with an inexpensive way to get high-quality finished prescription glasses.
They use the same high-quality materials, but because of their large volume, they offer a high discount because they have no additional overhead limits. Elastic glasses are made of high-quality titanium, one of the strongest metals on Earth. For you, that means your bent titanium glasses won't rust or break easily. Looking stylish and active, when you buy a pair of elastic glasses on 39DollarGlasses, your prescription glasses include full UV protection, and the thin and light lenses can be customized to your needs.