Understanding Bifocal Lenses As we grow older our senses tend to not be as sharp as they used to be. Changes in vision are one of the most “visible” alterations to the slow decline of our senses and it happens to be one of the most important ones too. Major loss to eyesight can change the way one carries on “business as usual” in their day to day life. Frustrations and irritation lead to the inevitable…one needs to have some type of vision correction available. The majority of adults at an age of 45 or more will start to require some type of visual aid (readers or reading eyeglasses) when reading or doing any close proximity work. In some cases this can continue to decline to a point where seeing what one is eating can be a problem. This is where bifocals lenses come in. Bifocals are plus lenses “added” to the spectacle to help with near work, which is why bifocal “additions” are called the “add”. Separate to the primary vision correcting lenses, the addition provides added benefit to the wearer that requires correction for close work. There are three types of lenses flat top, round top, executive and progressive For those having a minus addition a flat top is better, for those with round top a plus. The differences are in the way the lenses are cut. The round top will also produce the “image jump” phenomena so if this is a bother one might try the flat top. If the one is bothered by image displacement, use a flat top for minus lenses or a round top for plus lenses Executive lenses (Ben Franklin lenses) have no image jump and go all the way across the lenses; but they do have image displacement. These are now-a-days commonly used as kid’s bifocal lenses. The seize of the viewing area is much wider which makes desk work much easier.
The progressive lenses are commonly referred to as the “noline bifocals” As you look from the top of the segment to the bottom, the power “progressively “increases. So there is at the lowest portion of the lenses a reading area and in the center of the lenses there is a mid-distance viewing area and at the higher level the farthest viewing area. There are many types of designs in progressive lenses, but one of the newest types of lenses available now are what are called freeform lenses, which are more or lenses digitized progressive that give a much clearer and higher density viewing area than the traditional lenses.