The first number, or numerator, of the Snellen notation represents:

• A. the testing distance
• B. the letter size
• C. the near distance
• D. the patient's age

Answer: (A)

The numerator in Snellen notation represents the testing distance—the distance from the chart at which the patient was evaluated. In the United States, this is typically 20 feet (or 6 meters in metric charts). The denominator shows the distance at which a person with normal visual acuity would be able to read the same line; for example, 20/40 means the patient can read at 20 feet what a person with normal vision can read at 40 feet. The letter size on a given line corresponds to that line’s denominator, not the numerator, and the near distance or the patient’s age are not part of this notation.