Before the creation of bifocal lenses, people who have presbyopia had very few options. It is well-known that presbyopia requires patients to get vision correction at both distant and close ranges. Bifocals were available only in eyeglass lenses in those days. Those so called bifocal eyeglasses could offer both distance and close vision correction but they were much less advanced. Bifocal eyeglasses had thick lenses with a visible line down the middle. It was obvious that this design of bifocal lenses was far from attractive. Moreover, people wearing those bifocal eyeglass lenses would even suffer from giddy feeling while climbing up or down stairs.
The invention of bifocal contact lenses profoundly changed this scenario that presbyopic patients have another advantageous choice nowadays. Bifocal contact lenses available on the market come in more options than traditional bifocal eyeglasses. They can provide absolutely the same function as bifocal eyeglasses. People in their 40s bothered by focus difficulty can now choose bifocal contact lenses for more natural appearance. In fact, bifocal contact lenses have different designs.
The most common design is concentric lenses which have distance vision correction in the center and provide close vision surrounding it. In opposite, Asferic design lenses have the near correction at the center and distance correction around it. Another design is translating lenses, which have the distant correction located above the near correction center.
Bifocal contact lenses are also available in mono vision type. In this case, a lens does not offer both close and distance vision correction. Mono vision offers nearness correction in one eye and distance correction in the other. In most cases, the dominant eye should be given distance vision correction.
Another design is simultaneous vision lenses which enable presbyopic patients to focus on both near and far objects at the same time. These two kinds of vision correction lie in concentric circles unlike concentric design. With this design, the eyes can receive light from both near and far objects simultaneously.