1 Pair Photo Grey Lenses Invisible Bifocal Lens 1.56 Round Top Bifocal HMC Wholesale
Place of Origin: Jiangsu, China
Brand Name: Jian
Model Number: 1.56 Photochromic Invisible Round Top Bifocal HMC Lens
Lenses Material: Resin
Vision Effect: Single Vision
Coating: UC
Lenses Color: Clear
Diameter: 70/28 MM
Index: 1.56
Power Range: SPH: 0.00~-2.00, +0.25~+3.00 ADD: 1.00~+3.00
US$4.9/Pair, MOQ: 100Pairs(If you need, Could you please tell me through ebay message? I will give you a link, you can buy through the link. Thanks.)
Do you need bifocals?
Some time after age 40, you will begin to notice the symptoms of presbyopia, including that feeling that your arms "aren't long enough" to hold a newspaper or magazine at a position where you can read it clearly.
If you already wear prescription eyeglasses, this generally means you will need to begin wearing multifocal lenses to continue to see clearly at all distances.
While most presbyopes these days choose line-free progressive lenses, conventional bifocals and trifocals have some advantages over progressives. In particular, bifocal and trifocal lenses usually provide wider lens areas for reading and computer work than progressive lenses.
Also, there are many special-purpose bifocal and trifocal lens designs available, including special glasses for computers and for other tasks that require excellent intermediate and near vision.
One Lens, Many Functions
Multifocal eyeglass lenses contain two or more lens powers to help you see objects at all distances after you lose the ability to naturally change the focus of your eyes due to age (presbyopia).
Bifocals contain two lens powers; trifocals have three. Progressive multifocal lenses gradually change in power from the top half of the lens to the bottom, and thus contain many lens powers.
Though multifocal lenses usually are prescribed for adults over age 40 to compensate for presbyopia, in some cases bifocals are prescribed for children and young adults who have eye teaming or focusing problems that cause eye strain when reading.
In these cases, the bottom portion of the bifocal lens reduces the amount of focusing effort required to see near objects clearly.
Also, some research suggests wearing bifocals or other multifocal lenses may help control myopia in some children by reducing the focusing demands of reading and near work.
Regardless of the reason you need a prescription for near-vision correction, bifocals all work in the same way. A small portion in the lower part of the lens contains the power required to correct your near vision. The rest of the lens usually is for your distance vision.
The lens segment (or "seg") devoted to near-vision correction can be one of several shapes:
(1) A half-moon - also called a flat-top, straight-top or D segment
(2) A round segment
(3) A narrow rectangular area, known as a ribbon segment
(4) The full bottom half of a bifocal lens, called the Franklin, Executive or E style
Generally, you look up and through the distance portion of the lens when focusing on points farther away, and you look down and through the bifocal segment of the lens when focusing on reading material or objects within 18 inches of your eyes.
Trifocals have three points of focus - usually for distance, intermediate and near vision. The intermediate segment in trifocal lenses is directly above the near seg and is used to view objects at arm's length.
Computers are an excellent example of something that is in a person's intermediate zone. Motorists who need to see in the distance to drive, to see the gauges on the dashboard, and to read a map also would benefit from a trifocal.
The most popular trifocal styles are the flat-top and the Executive.
