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| Correcting Presbyopia with Segmented Lenses | Bifocal glasses are special glasses, which have a distance portion and a reading (near) portion. Usually to see objects that are far away from you you should look through the upper part of the lens, which is used for distance vision. And for reading you usually use lower part of the lens, which is intended for your near vision. Almost all bifocal contact lenses are designed in the same way. Like bifocal spectacle lenses, bifocal contact lenses can be made with the portion for distance vision on top and a portion for near vision at the bottom.
The contact lenses, which are designed in such a way, are called segmented lenses. Well, the design of bifocal contact lenses is similar with the bifocal glasses, but these lenses work in a little bit different way. When you wear bifocal glasses the spectacle lens in front of your eye you can direct your look through the part of the lens you need. But a bifocal contact lenses work in another principle. If you wear a segmented contact lens and your look changes from near to distance vision, the lens slightly moves on your eye to provide the near vision.
No doubt that to provide a distance vision the contact lens must move back again, and only than you will be able to see distant objects. Thanks to some designed features the lens move back in a proper way. For example, some contact lenses have a flat bottom edge, which allows the lower eyelid to stay in the position that is needed. One more variant is that the contact lens may be weighted a little bit on the bottom to prevent movement or rotation. The position of the lens is unstable, that’s why you should be patient before you get all the necessary skills. You may be required to visit your eye care ophthalmologist several times in order to adjust to your contact lenses. Alternating vision is provided with segmented contact lenses. They work in such a way: you see near things clearly when you look through the near-vision segment and you see distant objects easily when you look through the segment for distant vision.
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