How do reading glasses work?

Naturally, to see objects up close, the lens in your eye protrudes more to focus on close objects or writing. The process of focusing on close objects is called accommodation. When a person gets older, often around age 40, the eyes begin to lose their ability to focus on close objects. That condition is called presbyopia (from Latin, literally meaning "old eyes"). Anyway, the retina is the part of the eye that sends the image to the brain. The problem here is that light focuses behind the retina rather than on it.

Lenses to correct presbyopia and hyperopia (farsightedness) are convex lenses, meaning the lenses are the thickest in the center. They cause light to converge, meaning they cause light waves to bend closer together. So the eyeglasses adds enough power to the natural lens so when you look at things close up, the light rays converge into a point sooner, thus focusing directly on the retina.