Eye chart smaller towards the bottom of the chart. The person removes any glasses or contact lenses, and stands or sits a standardized distance from the chart (e.g., 20 feet for the Snellen chart). The person is then asked to identify the optotypes on the chart, starting with large rows and continuing to smaller rows until the optotypes cannot be reliably identified any more. The row in which the person can reliably identify symbols defines the visual acuity. One eye is tested at a time. Practically, this is accomplished by covering the other eye with a hand, piece of paper, or a
About the Mystery of the Letters Father respectively. The final chapters of the treatise engage in speculation about more general topics, including the history of mankind – whose key events are related symbolically to the sequence of vowels and consonants in the alphabet –, a discussion of Christology dealing with issues related to the Council of Chalcedon, and reflections upon the name of "Adam". About the Mystery of the Letters About the Mystery of the Letters (, "Peri tou mystēriou tōn grammatōn") is an anonymous Christian treatise containing a mystical doctrine about the names and forms of the Greek and Hebrew letters. It was probably written