Visual acuity refers to the clarity or sharpness of vision, which is the ability to see fine details. It is typically measured using an eye chart, where letters or symbols are displayed at a specific distance. The results are often expressed as a fraction, such as 20/20, indicating normal vision. A higher second number means poorer vision. Factors affecting visual acuity include eye health, lighting conditions, and distance from objects. Common conditions that can impair visual acuity are nearsightedness, farsightedness, and astigmatism. Regular eye exams can help detect changes in visual acuity and ensure proper vision correction if needed.