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Bifocal Reading Glasses
After the age of 40 most of us who can't use "readers" will need bifocal reading glasses. These glasses offer vision correction for those who have a need for glasses or contacts even before middle age brings the advent of presbyopia. The problem of presbyopia. Presbyopia is sometimes mistakenly called "farsightedness," but it's actually a condition in which the lens of the eye thickens and it becomes difficult to focus on objects closer than 18 inches (45 cm) in front of the eyes. Your distance vision may stay the same, get worse, or get better, but when you develop presbyopia, you will probably need lens for reading. Bifocal vision correction for reading and driving. Bifocal lenses offer correction both for close vision, used for activities like reading, and for distant vision, used for activities such as driving. Bifocal reading glasses make it possible to drive and read without changing glasses, and give you one less pair of glasses to keep up with. And, unlike, say, eye wear from the 1950's, bifocal lenses can be ground to look like the lenses used in glasses for younger people. The lenses that look best actually correct vision best. Here's why. Shapes of vision correction in bifocal lenses. The segment of the lens that allows for correction of near vision can be any one of several shapes: The idea is that you look down at objects on a table close to your eyes, so you need near vision correction in the bottom of your lens. You usually look up when you are looking out to see something in the distance, so you have distant vision correction in the top of your lens. The way lenses used to be made, however, there was a sharp line between the areas of the lens used to correct the different distances. When you looked up from your newspaper to see something across the room, for instance, the room seemed to "jump" as you’re center of vision passed over the line in your lenses. Nowadays, fortunately, lenses for bifocal reading glasses can be ground to be progressive. No-line Bifocal Reading Glasses. Progressive lenses for no-line bifocal reading glasses offer vision correct that gradually transitions from the prescription for distant vision in the top half of the lens to the prescription for reading and other near vision activities in the bottom half of the lens. When you are reading through your progressive bifocal glasses and, say, you hear someone at the door, you see a smooth transition of focused images as your eyes move from looking at the objects directly in front of you to looking at the objects at a distance from you. Most people who need bifocal reading glasses find progressive lenses much more comfortable than their alternatives.
Not just bifocalsSometimes you need one kind of vision correction for distant vision and another to see objects less than 18 inches away from your eyes, but you need a third kind of correction for objects that are more or less exactly 18 inches from your eyes. For this kind of vision correction it is possible to obtain trifocals. Trifocals are designed to correct your focus for objects about arm's length away from your eyes. You can make a rough estimate of whether you need trifocals just by holding something in your hand, stretching out your arm, and trying to see it clearly, but you can also tell by reading your prescription for your bifocal reading glasses. If your near vision correction is more than +2.00, then you probably will need bifocals. And rimless bifocal Reading Glasses, too. Many people who have to wear bifocals don't want to call attention to their glasses. One way to do that is to choose rimless lenses. In rimless glasses, the temples of the glasses are attached directly to the lenses rather than to a frame. Rimless styles are available for progressive lenses. |