Why Do I Need Bifocal Lenses?

Benjamin Franklin invented bifocal lenses in the eighteenth century. Since then, bifocals have become the standard way to maintain crisp, clear vision as we age. Why do we need bifocals to see well?

Eyes focus an image onto a sensory net called the retina. The retina is in the back of the eye like film or an electronic sensor in a camera. The lens is resilient clear tissue that focuses the image on the retina. When looking at a close object, muscles in the eye allow the lens to thicken. To focus on an object farther away, muscles relax and the lens flattens. With age, focusing becomes more difficult.

The first symptom of difficulty focusing may be eye strain or headache while reading. It becomes difficult to see at close range. Most people need reading glasses by the time they are 45 years old. These symptoms are delayed for myopes (those who are nearsighted). Myopia is the tendency of some people to see well up close, and not see well at a distance. Myopes may not need reading glasses.

When the loss of the ability to focus affects distance vision, another type of correction is necessary. Lenses for distance vision are different from reading lenses. Ben Franklin's advancement was to create a single lens with two different strengths so that the wearer need not change glasses when looking near and far.

Later advancements increase the utility of glasses further. The tri-focal lens includes three different strengths of lens in one pair of glasses for seeing near, far and at a mid-range such as when reading a computer monitor. Progressive lenses have infinite variation from reading distance to vision. An added benefit of progressive lenses is the absence of the lines visible in bi or tri-focal lenses. Finally, bifocal contact lenses use ultra-modern optical and manufacturing sciences to give contact lenses the same dual strength capability of bifocal glasses.

Your optometrist, ophthalmologist and optician can work with you to determine which type of lens is best. Important considerations include the profession of the wearer, sports, the kind of work (close up work, computing, design), comfort and appearance.