Bifocal Lens - With a Line
Bifocal prescription glasses are made especially for those individuals that are nearsighted and farsighted at the same time. Such individual with dual power in their eyes opt for those glasses online that are best fit for presbyopia.
In bifocal vision, you need two separate prescriptions for clear vision. These include one for far vision and the other for seeing objects clearly up close. Due to the imaging principle of the lens, even a half-piece lens can still present a complete image, and the two images do not interfere with each other.
However, the intermediate distance of bifocal glasses has poor visual effect. Produce a “image jump” phenomenon and have a poor appearance. Due to its own major shortcomings and the popularity of progressive lenses, bifocal lenses have been basically eliminated.
Progressive Lens - No Line
Progressive lenses are developed on the basis of bifocal lenses.In addition to not having to remove the glasses, the wearer can also move the line of sight gradually between the upper and lower focal lengths when observing the far/near objects. The eyeball needn’t constantly adjust the focal length, and there is no obvious dividing line between the two focal lengths.
Progressive lenses accommodate for both near and far vision by adding a unique lower lens with ADD vision value for reading and near vision, without the obvious line of bifocal lenses. They are more than just a defined near and distance correction in one lens, but progressive eyeglasses provide a smooth transition from distance through intermediate to near, with all the in-between corrections included as well.
For the crowd
Progressive lens is suitable for the following crowd:
Anti-fatigue lenses for adults -- for teachers, doctors, and people who use too much proximity and computers to reduce visual fatigue at work.
Progressive lenses for middle-aged and elderly -- a pair of glasses which is easy to see near and far.
Advantages of Progressive Lenses
* It provides clear vision at all distances (rather than at just two or three distinct viewing distances).
* The appearance of the lens is the same as that of the single lens, and no dividing line of degree change can be seen.
* It eliminates bothersome "image jump" caused by bifocals and trifocals. Comfortable to wear and easy to adapt.
* The degree of the lens is gradual, and the change from far to near increases step by step, which will not produce the fluctuation of eye adjustment and will not cause visual fatigue easily.
Notices for wearing
* When choosing a pair of glasses, you'd better choose a large frame. Because the lens is divided into far, middle and near zones, only large frames can ensure a wide enough for near zone. It is best to use a full frame, due to the larger the lens, the thicker the edge of the lens, the full frame groove can cover the thickness of the edge of the lens.
* Generally, it takes about a week to adapt, but the length of the adaptation period varies from person to person. When you are dizzy, you should walk slowly. Since both sides of the lens are astigmatic disorder area, it is not clear to see objects on both sides through the light of the eyeball, and it is necessary to turn the neck and the eyeball to see at the same time.
* When going downstairs, the glasses should be lower, try to see from the distance zone.
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