Think of the eye like a camera. When you take a distance picture the camera automatically changes focus to distance. When the eyes look at near they automatically focus at near. At 20 years of age we have 20 units of focusing (diopters), more than enough to sustain focusing at 16 inches. However, as we get older we begin to loose the focusing power. By age 40 we only have 5 units of focusing and we need to sustain 2.5 units. The first thing we do is push the material away. An arm stretch would do the trick. As it gets worse the blur at near gets worse. Eyestrain and/or headaches ensue. We need a different prescription at near than far. If you are myopic you may find that you see perfectly well without your glasses. If you are farsighted and you develop this age related presbyopia you are getting a double whammy. Glasses for distance and near. If you are emmetropic (no error at distance or near), you just need reading glasses.
From 40 to approximately 57 you will continue to loose the focusing power if you use the glasses or not. The loss in focusing is not muscular. The lens in the eye looses its elasticity, thus, loosing its ability to change focus. The glasses will help you see clearly and comfortably. There is no reason to fight. It is more important to get a good pair of glasses. Remember, those glasses are the first thing everyone sees – it a fashion statement. Also, like clothing – quality counts. Good frames stay in shape and are durable. Lastly, the optics should be first rate to give you the vision you deserve.
Bifocals were originally designed by Ben Franklin. They have two distinct areas; one for distance and the other for near. When you are in your mid-forties, bifocals provide an adequate range of vision. However, as you approach the 50s and you loose more focusing power you will loose the mid-range and may need a trifocal. All bifocals and trifocals have distinct areas of vision and thus have a line. The line may be visible or invisible. Visible lines provide a smaller transition zone and thus have a more useful lens than invisible bifocals. Invisible bifocals are made by blurring the transition zone from distance near. They should only be used in someone who needs good distance optics and a small reading area, e.g., to see the menu or price tags. We usually reserve bifocals for special occasions in which our patient is not walking with them, and they require perfect optics for distance and near.
Usually a better choice is a progressive lens. Progressive lenses may be thought of as Zoom lenses. The power gradually changes from distance to near. There are no lines. The power is variable. To make a progressive lens part of the lens, the peripherally, is blurred to obtain the variable power. Thus, there is a channel for reading. The stronger the reading prescription the narrower the clear zone. Each brand of progressives is designed differently, i.e., all progressives are not the same in design or optics. Depending on your needs we will select best progressive for you. Some are biases for distance viewing, others for near, while still others for computers and reading. Let us know your needs and we will select the best lens for you. Progressive lenses must be fit accurately to make sure that both eyes are in the channel and are at the correct height. Some are designed for the computer.
Bifocal contact lenses better than they use to. They are not perfect but work for approximately 60% of the the over 40 population. Based on your needs we will determine the best type for you. Often time bifocal contact lens wearers can be fit with mono-vision. One eye for near and the other for distance. Sounds like it shouldn’t work, but to everyone surprise it is successful in about 80% of the properly selected patients. With a few simple tests we can find out if you are a candidate.