In the aspheric design, the near and distance prescriptions are both near the pupil. In this example of the concentric design, the near prescription is in the middle and far is on the outside, but they can also be reversed. In this example of the translating design, the near prescription is on the bottom. Bifocal contact lenses are designed to give good vision to people who have a condition called presbyopia . The key sign that you're developing presbyopia is that you need to hold reading material, like a menu, further from your eyes to see it clearly.
Bifocal contacts are available in both soft and rigid gas permeable materials.
Today s bifocal contact lenses are even available in a disposable or frequent replacement wear regimen. That means you can have the convenience of throwing the lenses out at specified intervals and replacing them with fresh, new lenses. Disposable bifocal contact lenses first became readily available in 1999. Other designs work more like progressive eyeglass lenses, where the different prescriptive powers are blended on different parts of the lens. Your eye learns to differentiate the proper power for the correct distance.