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Eyeglasses, Sunglasses, and Magnifying Glasses
It is common for pharmacies today to carry nonprescription eyeglasses, sunglasses, and magnifiers. We hope this review will assist consumers with valuable information about these eye products.
Nonprescription eyeglasses
Nonprescription eyeglasses are primarily for persons who can no longer read fine print. Although over-the-counter (OTC) glasses do not appear to harm vision, if they are not appropriate for a person's eyes, they can cause eyestrain after prolonged use.
Most pharmacies offer standard and bifocal lenses, and some vendors also offer transitional lenses that lighten up indoors and darken when outdoors.
The quality and durability of OTC eyeglasses varies widely. Cheap models -- costing as little as a few dollars -- may have lenses that scratch easily and distort vision. Expensive models--costing $50 or more--may incorporate some or all of the desirable characteristics of high-quality prescription lenses.
Manufacturers rate the power of nonprescription glasses from weakest (1.0) to strongest (3.5). When making a selection, the customer tries on eyeglasses and reads fine print while standing 12 to 14 inches from the print. The customer keeps trying on glasses with different power ratings until the print comes into sharp focus. Suppose, for example, the print comes into focus when the customer is wearing eyeglasses with a power rating of 2.0. The customer then knows that a 2.0 rating is correct and can select from styles with that rating.
In some cases, customers may also be asked for the "pupillary" distance. This is actually the interpupillary distance, the distance between the pupils (the openings) of the eyes. This distance is usually measured in centimeters.
We do not recommend nonprescription glasses as a permanent solution to significant eye problems because they usually are not as accurate as prescription lenses. In addition, the use of OTC glasses could lead to the postponement of an eye examination that could reveal a serious underlying problem. However, OTC glasses are okay to keep as "backups" for times when prescription glasses have been misplaced or are being repaired.
http://www.medicinenet.com/eyeglasses_sunglasses_and_magnifiers/article.htm