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.
Early glasses
The first inventor of wearable glasses is not known. However, it was the Romans who first discovered the use of glass to enhance their ability to see small words, creating small magnifying glasses with spheres. The first known wearable glasses in history appeared in Italy in the 13th century. They were used mainly by monks, and became popular little by little during the Renaissance, as the technology improved. As their popularity grew, the Italian glasses spread throughout Europe, mostly within reach of the wealthy. Because learning was a prized attribute during the Renaissance, glasses were a status symbol of wisdom and prosperity. With the temple extending above the ear, the glasses are no longer required by hand.
Reading Glasses
At present, there are two prescriptions for reading glasses. One is to adjust the power of glasses with clear objects at close range, plus 1/3 of the power for adjustment. The other is to use low power that can see close objects clearly. The practice of many elderly people has proved that the latter one is better between two methods.
ATTCL Retro Polarized Night Driving Glasses
These glasses have metal frames. The metal frame uses an aluminum-magnesium alloy structure, strong and light. While you'll see them available in a variety of colors, you'll still have to choose the night vision option if you want to buy night driving glasses. The anti-glare yellow night lens is designed to filter 20 percent of glare at night.
Why do you need low bridge glasses?
The glasses always slide in front of the nose. No one wants to keep putting their glasses back in place, especially in a conversation. Your glasses will slide down your nose, in other words, they won't sit on the bridge of your nose, and the frames will hit your cheeks, which may give you a cheek rash. The glasses move when you smile or laugh. The lenses rub against your eyes/eyelashes.
Color process of Contact lenses
Pigment printing process
It refers to the direct printing of pigments or patterns on the inside of the lens and then drying, which is the main production process of poor-quality chromatic contact lenses. Usually, small factories and small workshops use this method. The lens is being phased out because the pigment can easily seep out from the surface during wearing, causing discoloration and staining, and irritation to the eyes, which is a big risk.
Pigment build-in process
To be specific, the lens made by sandwich technology is a three-layer structure, the front and rear are colorless transparent layers, and the middle is a colored layer. After the processing of sandwich technology, the color layer is wrapped in the middle of the front and rear transparent layer, so that the pigment will not contact the eyes, which will not cause irritation and injury to the eyes. The downside of this process, however, is that the lenses are slightly thicker than normal contact lenses and are less oxygen-permeable, so they are not suitable for long-term wear.
The pressed film manufacturing process
This is a relatively new method of a similar sandwich process, and the color (pattern) is also made between the front and rear layers of the lens. But the color (pattern) is used to fill in the film process. During lens curing, the pigment seeps into the material instead of sticking to the surface. It feels as if the lens is covered in color within a single layer. This reduces the middle layer and makes the lens thinner, which naturally makes it more comfortable and permeable to oxygen.
Types of Bifocal Lenses
Flat top: It is a kind of common bifocal lenses. The lower part of the lens is present in the shape of a half-moon or the letter D on its side. The upper part and the lower part of the lens can be clearly distinguished from each other. The patient using such a bifocal lens has the choice of choosing the length of the lower segment which is either 25 mm or 28 mm.
Round seg: the second type of bifocal lens we want to mention is the round seg. The segment is either 22 or 24 mm in length and it provides more are to adjust between the two different types of vision easily. This type is very rarely used nowadays.
Blended: this type of bifocal lens has the lower part of the lens in a round shape and the edges of the lens are blended with the upper lens making the lens appear as one.
