An optometrist is one who measures vision. My prescription calls for an additional 2 diopters for near vision. As children, many of us get the idea that an eyeglass is a kind of magnifying glass. If you pick up a pair of eyeglasses and hold them at arms length, or if you look at someone else's eyeglasses as they are wearing them, what you are most likely to notice is a slight magnifying or reducing effect. But this is quite incidental.
Nothing is perfect.
In addition to its intended effect, every device has other effects as well. Everything is always a compromise design. In the case of eyeglasses, the intended effect is focus correction. In addition, eyeglasses have small unwanted effects including magnification or reduction, distortion, color fringes, altered depth perception, etc. The ideal way to correct focus would be to alter the shape of the lens of the eye itself.