This test consists of four optotypes (test symbols): the outlines of an apple, a pentagon, a square, and a circle. Because these four symbols can be named and easily identified as everyday, concrete objects ("apple", "house", "window", and "ring"), they can be recognized at an earlier age than abstract letters or numbers can be. This enables preschool children to be tested for visual acuity long before they become familiar with the letter and numbers used in other standard vision charts.