Single Vision for Distance

Single vision lenses are just what its name says, a lens with one prescription throughout the entire lens. If you only struggle with distant sight (or close-up sight), you probably need single-vision lenses.

A person wearing a pair of eyeglasses with a minus prescription is myopic and is known as being nearsighted. A person wearing pair of eyeglasses with a plus prescription is hyperopic and is known as farsighted.

Single vision lenses have the same focal power throughout (top to bottom) and can be used to correct nearsightedness, farsightedness, astigmatism, or a combination of these disorders. Most people who wear glasses before the age of 40 have single vision lenses. Single vision lenses are available from framesandcontacts.com in indexes of refraction from 1.50 (CR-39), 1.59 (polycarbonate), 1.60 high index, 1.67 high index and 1.74 high index.

For Reading Only

Do you need prescription reading glasses? Sometime after age 40, you will begin to notice the symptoms of presbyopia, including that feeling that your arms "aren't long enough" to hold a newspaper or magazine at a position where you can read it clearly

Single vision reading lenses have the same focal power throughout (top to bottom) and are used to correct nearsightedness, with or without astigmatism. Single vision reading lenses are available from framesandcontacts.com in indexes of refraction from 1.50 (CR- 39), 1.59 (polycarbonate), 1.60 high index, 1.67 high index and 1.74 high index.

Reading glasses can be custom-made, or they can be purchased "ready-made" usually at a pharmacy or department store. A major drawback to purchasing ready-made ("drugstore") reading glasses is that they are essentially "one-size-fits-all" items. The prescription is the same in both lenses, and the location of the optical center of the lenses is not customized for each wearer. Most people do not have exactly the same prescription in both eyes, and almost everyone has at least a small amount of astigmatism correction in their prescriptions.

Headaches, eye strain, and even nausea can result from wearing reading glasses that are too far off from your actual prescription or that have optical centers too far away from the center of your pupils. If you experience these problems, visit your eye doctor for a customized reading glasses prescription.

Bifocals

Bifocal lenses have two parts: the upper part normally used for distance vision and the lower part used for near-vision tasks such as reading. Many people after reaching age 45 develop a condition called presbyopia, which is deterioration in the ability of the eye's natural lens to expand or contract in order to focus on close objects.

Regardless of the reason you need a prescription for near-vision correction, bifocals all work in the same way. A small portion in the lower part of the lens contains the power required to correct your near vision. The rest of the lens usually is for your distance vision. The segment for near-vision correction usually has a half-moon shape and is sometimes referred to as a flat-top.

Generally, you look up and through the distance portion of the lens when focusing on points far away, and you look down and through the bifocal segment of the lens when focusing on reading material or objects within 18 inches of your eyes. Do you need bifocals? Sometime after age 40, you will begin to notice the symptoms of presbyopia, including that feeling that your arms "aren't long enough" to hold a newspaper or magazine at a position where you can read it clearly. If you already wear prescription eyeglasses, this generally means you will need to begin wearing multifocal lenses to continue to see clearly at all distances. If you want to wear a multifocal lens without visible lines, progressive lenses usually are your best choice.

Progressives (no line)

Multifocal Lenses, also called Progressive lenses have corrective powers change progressively throughout the lens. They are a convenient alternative for people over 40 years old who require separate glasses for distance and near vision. A wearer looks through the top portion of the lens for distance vision, middle portion for intermediate vision, and the lower portion for reading or close work. Each area is blended invisibly into the next, without the lines that traditional bifocals have.

Multifocal Lenses provide a smooth transition from distance through intermediate to near, with all the in-between corrections included as well. This constant graduation of the prescription means that you can look ahead through the top section to see in the distance, drop your gaze downward slightly through the middle section to view objects in the intermediate zone (around 65 centimeters away), and drop your gaze further down to read and do fine close up work comfortably. There are certain requirements on optical frames for multifocal glasses.

Progressive, or no-line bifocals, provide all the benefits of bifocals but add the feature of continuous clear vision at all distances, including mid-range distance (arm's length). Progressives have the cosmetic advantage of appearing to be single vision lenses, so they never reveal that the user wears bifocals. Progressives are available in all lens materials.

It's important to note, however, that the first time you wear progressive lenses, you may notice a soft blur in your peripheral vision through the lower half of the lenses, to the right and left of the intermediate and near zones. If this occurs, the sensation typically will go away after a week or two of full-time wear.