Hold the chart 14 inches from your face, and study the chart to find the smallest line of print that is clear and easy to read. The number beside that line corresponds to the strength, or diopter, of glasses needed.
Reading glasses are sold in diopters ranging from 1.00 to 4.00, increasing in increments of 0.25. Some diopter charts show only increments of 0.50 diopters, so it's a good idea to bring reading material along and test glasses 0.25 diopters above and below the level suggested by the chart. The best pair of glasses to buy is the weakest strength that allows comfortable reading of the material at a normal reading distance. Reading glasses are available without prescriptions at pharmacies and in the health care sections of larger stores.
Most people begin to need reading glasses in middle age, when the lens of the eye becomes less flexible and the ciliary muscles that control the shape of the lens weaken. As these changes take place, the eye becomes less able to accommodate itself to seeing objects close-up, a condition called presbyopia. Reading glasses provide the close-up focus that an eye can no longer perform unaided.
Before purchasing reading glasses, schedule an eye examination to be sure that any changes in vision are not due to a more serious condition. Reading glasses are not a substitute for prescription lenses or regular care from a professional.