Bifocal literally means “two focuses.” It is meant to describe eyeglass lenses that enable the user to see clearly at two different distance ranges through one lens. Benjamin Franklin is credited with inventing the first bifocal lens by gluing two lens halves from two different lens prescriptions together. Bifocal glasses are used for many reasons, the main reason being for Presbyopia.
Presbyopia is a vision condition in which the crystalline lens within the eye looses its flexibility. At about 40 years of age, we perceive this as increasing difficulty with clearing objects the closer we bring them toward our eyes, especially in low lighting levels. Bifocals have an additional power on the bottom part of the lens to aid in close up focus, enabling clarity at both distance and near with one pair of glasses.
Progressive Multifocal Lenses
Like bifocal glasses, progressive multifocal lenses enable the user to see clearly at different distance ranges through one lens. A progressive lens gradually changes power from the top of the lens to the bottom, giving a smooth transition from distance vision to intermediate/computer vision to near/reading vision. Progressive multifocal lenses do not have lines or segments and have the advantage of offering clear vision over a large range of distances, not limiting you to two distances as with bifocal lenses.
However, not all progressive multifocal lenses are created equal. They come in a variety of designs and styles. Since the overall design of a progressive lens tends to distort the edges of the lens, it is in one’s best interest to choose a high quality, wide mid-range and reading area. This will minimize adaptation as well as provide the best overall comfort and clarity in all situations. It is important to know that there are four main factors that determine success with progressive multifocal adaptation:
- The Brand – Higher-end progressive multifocals have advanced optical designs allowing for smooth adaptation and enhanced vision and comfort. Rely on the advice of your optician as to the best choice in lens design for you. Your vision is something you use everyday. Make sure it is not something you have to think about everyday.
- The Measurements – Precise measurement is crucial to your success with progressive multifocal lenses. Improper measurement is the primary reason for non-adaptation to progressive lenses. It is important to ensure that you are looking through the optical center of your new lenses. This will allow you access to your clearest and most comfortable vision.
- The Frame – Your choice in frame size as well as proper adjustment of your frame can determine your comfort level with your new lenses. If you are having difficulties adjusting, confirm with your optician first that your frame is properly fitted to your face. A simple frame adjustment could mean the difference between frustration and effortless vision.
- The Motivation – Oftentimes, patient motivation is the determining factor in adaptation to these lenses. You should expect an adjustment period of at least two weeks. If you give yourself the time to wear your new glasses on a consistent basis, you will adjust.