How do eyeglasses affect the properties of light?

Eyeglasses primarily function to help focus light onto the retina, enhancing vision for those with refractive errors such as nearsightedness or farsightedness. The lenses in eyeglasses are designed to bend (refract) light rays in a specific way so that when light passes through them, it converges (or diverges) correctly onto the retina, allowing for clearer vision. This focusing capability is crucial for ensuring that images appear sharp and well-defined, significantly improving one's ability to see objects at various distances.

In contrast, while some types of eyeglasses may provide UV protection or have features that could influence brightness perception, the primary role of standard prescription lenses is to adjust the way light is directed to the eyes, thus reinforcing the concept that they help focus on light.