A Visual Acuity Chart with Geometric Gradation and Logarithmic Notation

Since the principle that optotypes on a test chart should follow a geometric progression was advocated by Green1 in 1867 and developed by Sloan2 in 1959, many such test charts have been designed.3,4 However, none of the charts has an exact logarithmic notation. In 1959, one of us (T.-Y. M.) designed a chart with both geometric gradation and logarithmic notation (Figure).5 This chart has been used in China for many years, and we have found it convenient for clinical use at various distances and for establishing statistics in vision.