The Shellen chart as a test of visual acuity

Summary An analysis of the mistakes made by 100 boys in reading the letters on a Snellen Chart reveals great differences in legibility between letters of the same size. This is found to depend on the shape and familiarity of the letter and its similarity to other letters. Whether a test of visual acuity consists of two-point discrimination or the perception of meaningful shapes, mental organization is a deciding factor in determining the response. While oculists are interested in the part played by the eye in vision, psychologists direct attention to the part played by the mind.Based on a paper read at the British Association Meeting at Newcastle in September, 1949.