This measurement reflects the amount of power necessary to focus images directly on to the retina. In addition, the eyeglass prescription may also contain the following measurements. This number measurement reflects the extent of the nearsightedness or farsightedness. By federal law, an eye doctor is required to provide an eyeglass prescription, following an eye exam, at no extra cost. In addition, under federal law, you have the right to a copy of your eyeglass prescription, so that you can shop for the best value in eyewear.
Convex lenses are thickest in the center, like a magnifying glass.
Cylindrical lenses curve more in one direction than in the other and are often used to correct astigmatism. Special measurements will need to be taken of the curvature of the eye. In addition, the physician will determine if the eyes are too dry for contact lenses, and if there are any corneal problems that may prevent a person from wearing contact lenses. Trial lenses are usually tested on the eyes for a period of time to ensure proper fit. Although, many eye care specialists will give you a copy if you request one.