ABSTRACT
This chapter is a comprehensive reference manual providing information on the Snellen Chart, which is an objective test of visual acuity. This is measured through the ability to identify small letters presented at high contrast from the background at a specified distance. A number of alternative forms of the Snellen Chart are available. These make it possible to assess people with very limited or no literacy, including children and people with cognitive impairment. If visual acuity screening is conducted using a Snellen Chart a significant number of people will have “false positive” results because of refractive problems. A brief history of the instrument's development is provided, along with a description of item content and administration/scoring procedures. Psychometric properties are reviewed and a critical commentary is provided. Key references are cited and in most cases the actual scale is included, giving the reader easy access to the instrument.
