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most associated with high prescriptions. The aspheric lens eliminates distortions, thereby providing sharper optics than in a conventional lens.

Presbyopia eventually afflicts most of us. We usually start noticing it in middle age. Small print becomes blurry, and soon our arms become too short, as we pull our reading material further away. This is due to a gradual loss of flexibility to the lens, so it cannot accommodate and various distances. The most common correction for presbyopia is multifocal lenses.

Bifocal lenses have two main corrections. The main part of the lens is corrected for nearsightedness or farsightedness and the bottom part has the prescription for reading or close work. Traditional bifocals have a distinct line on the lens.

If you do not like the look of the line, progressive lenses may be an option. They are also known as no-line bifocals. These lenses have a gradual transition between the two prescriptions, rather than a distinct, noticeable line. Progressives allow you to focus at various distances, including intermediate ranges. When you choose a frame, be sure the height of the frame is large enough so the reading portion is not cut off.

Single vision reading glasses are another option. They are available in full-frames or half-eyes, which are smaller frames that sit lower on the nose. They can be filled with your prescription, or you can purchase them pre-made, such as those found in drugstores. While they are inexpensive, they are not ideal for everyone. They do not accommodate those with prescriptions that are different in each eye, nor do they customize the optical center for each eye.

Other Lens Features

Photochromic lenses used to be known as PhotoGray, glass lenses that darken outdoors and lighten indoors. They are available in conventional plastic as well as high-index and multifocal prescriptions. If you plan to wear them while driving, note that they will not darken in the car, as the windshield blocks the UV rays which activate the lens change. Also worth noting is that they do not change as quickly as suggested by television commercials.

Anti-reflective coatings are ideal for wearers of high index lenses and who are bothered by glare. The layers of metal oxides applied to the lenses reduce reflections and block glare. They do tend to scratch and smear fairly easily, so special care is essential. Do not coat photochromic lenses with anti-reflective coating, as it can impair their ability to change.

While no material is scratch-proof, a scratch coat makes lenses more resistant to scratches. To avoid scratching your lenses, do not use paper products such as tissues or paper towels to clean your lenses. Keep your glasses in a case when not wearing them, and do not lay them on surfaces with the lenses down.

Learn more about this author, R. M. Ziegler.
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