Visual acuity refers to the clarity or sharpness of vision and is typically measured by the ability to discern details of a visual stimulus at a specific distance. It is often assessed using a Snellen chart, which consists of rows of letters or symbols of decreasing size. Visual acuity is an important aspect of overall eye health and is used to diagnose and monitor conditions such as nearsightedness, farsightedness, and astigmatism. Researchers in this area may study factors that affect visual acuity, such as age, genetics, and environmental influences, as well as develop and test interventions to improve or preserve visual acuity.