Few people do not have the same prescription in each eye, but the lenses put in stock reading glasses maintain the same power. Many individuals have an astigmatism, which cannot be corrected by using stock reading glasses. Using reading glasses to correct an astigmatism could lead to blurry vision and nausea. Stock reading glasses, especially the lower cost variety found in drugstores and superstores, use low quality plastic lenses that may not be formed properly. These plastic lenses could be blurred or have bubbles that impair your vision. This is why it is best to see your eye doctor to determine which degree of readers you need and if stock reading glasses are good or if you require custom reading glasses instead.
Bifocal reading glasses are only glasses that have clear lenses at the top and reading lenses at the bottom. With bifocal reading glasses, you can look straight through the top portion of the lens and still have reading magnification when you look down. Half-eye reading glasses are flat on the top of the frame and are designed to sit down low on your nose so that you peer down through the lens when reading. Afterwards, when you look up, you do not see through a lens so objects in the distance are not blurred. Full-eye reading glasses are good when you spend a long time concentrating on material close-up. When you look up from reading, objects in the distance appear blurry.