Presbyopia, which is the visual inability of the lens of the eye to focus on objects that are close, may take years to develop. Patients usually begin to show symptoms of presbyopia in their early- to mid-40s. Bifocal or multifocal eyeglasses will provide patients with presbyopia the ability to see clearly at all distances.
Bifocal and multifocal lenses allow patients to focus on both nearby and distant objects without the need to switch glasses or contact lenses. More than one prescription is combined into a single lens of the eyeglass.
Types of Eyeglass Lenses
Bifocal eyeglass lenses contain two lens powers. prescriptions (distance-viewing at the top of the lens and near-viewing at the bottom) with a sharp separation in the middle.
Trifocal eyeglass lenses have two lines and contain three powers - distance, near, and intermediate.
Multifocal eyeglass lenses are called Progressives or No-Lines. They look better cosmetically because there is no bifocal line. They let you see at distance, near, and all distances from infinity to 14 inches by just dropping your eyes to the proper area in the lens. Another advantage of a Progressive is that it prevents any "jump" of the image that happens in lined bifocals when looking below the line.
The advantages of a bifocal or multifocal lense prevent the "jump" in vision when glancing from a nearby object to one further away. Bifocal and multifocal lenses do take some time for adjustment, but once the adjustment has been made, patients never want to go back to separate regular reading and distance glasses.
