The exact definition of "eyesight" is difficult to pin down. Depending on which dictionary or other resource you check, it can mean "ability to see," "the sense of seeing," "vision," "range of sight" or "view." Often, the terms "eyesight" and "visual acuity" are used interchangeably. Vision is a broader term than visual acuity or eyesight.

Eyesight starts when light meets the eyes. After that, all kinds of things are set into motion. Light signals travel along this visual pathway to reach the brain. Light from an outside source, such as the sun or an artificial light, either travels directly toward you or bounces off another object, and then travels toward you.