An eye chart is a tool used by eye care professionals to measure visual acuity, which is the clarity or sharpness of vision. The most common type is the Snellen chart, featuring rows of letters that decrease in size. Patients read the letters from a specific distance, usually 20 feet, to determine how well they can see. Eye charts can also include symbols or numbers for those who cannot read letters. The results help identify vision problems and guide the need for corrective lenses or further examination. Regular eye tests using an eye chart are essential for maintaining good eye health.