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What is no line bifocals lens (progressive multifocal lens)?
No line bifocals lens (progressive multifocal lens) is a lens that
upper part is used to look far, the middle is used for medium distance and the bottom is used to look at the near.
Pros and cons
Pros: The power of no line bifocals lens changes gradually over the progression zone from the distance power at the top to the near power at the bottom, which has many advantages over ordinary lenses.
1) The lens looks like a single vision lens and does not see the dividing line of the degree change. Not only is it beautiful, but more importantly it protects the wearer's age privacy (for reading glasses wearers), and there is no need to worry about leaking the age secret by wearing a mirror;
2) Since the change in the degree of the lens is gradual, no image jump will occur. Comfortable to wear and easy to adapt. There is no adjustment fluctuation, which is not easy to cause visual fatigue;
3) It provides clear vision at all distances rather than at just two or three distinct viewing distances.
Cons: Generally speaking, No line bifocals lenses are the lenses of choice for virtually anyone who needs corrective lenses to see distant objects clearly because of combinations of nearsightedness, farsightedness, astigmatism and presbyopia.
1) Initially wearing progressive multifocal glasses may appear: slight dizziness, walking and shaking, exercise caution when going up the stairs;
2) The sense of space changes, the distance of the object is judged, and the sense of depth changes;
3) The object is obscured by looking at the object through the blurred vision area around the lens.
1) It is not advisable for the first wearer to drive immediately and do strenuous exercise. When you are close, you need to turn your eyes down and your eyes are slightly uncomfortable;
2) Therefore, when the first wearer looks at things, turn the head more, turn the eyeball less, and try to use the far-field, near-use, and medium-distance areas to see the object.
Types of no line bifocals lens we provide:
External Progressive lens vs. Inner Progressive lens
External Progressive lens is also called the front surface design progressive lens, which is to put the function side of the power changing zone on the front surface of the lens, farther away from the eye.
The Inner progressive lens, also known as the posterior surface design progressive lens, we can know from the name, this progressive lens is to put the function side of the power changing area on the back surface, closer to the eye.
Pros and Cons
1) The width of the field of view
The inner progressive zone is closer to the eye, and the external progressive zone is farther away from the eye. You can do such a small experiment: when the finger loops into a circle, when you put it in front of your eyes, the field of view seen through the circle is wider; on the contrary, the field of view is narrower. From this, we can easily see that the width of the inner progressive view is wider than the external progressive lens;
2) Manufacturing Process
External lenses are usually 100 percent digitally surfaced or ground. These lenses are computer designed with small changes to allow both eyes to work together. They often incorporate the fact that you have a dominant eye. This customizes the prescription for you as well as the frame you desire. As expected, these lenses are more expensive and need 5-7 days more to manufacture. It always needs a skilled optician to fit them to frame properly;
3) Eye adjustable ability requirement
The inner progressive lens is closer to the eye, and the eye needs to adapt more quickly than that to the external progressive lens when the wearer change sight directions.
For middle-aged and elderly people, their Eye adjustable ability is weaker than the younger people. Therefore, it may be more difficult for them to adapt to the lenses.
In summary, for those who have a strong Eye adjustable ability and need a wide field of view, we can recommend internal progressive lenses.
For those customers whose Eye adjustable ability is weaker, we can recommend external progressive lenses.
If it is a first-time wearer, and ADD value is a small, it will be better to wear external progressive lenses.
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