What does the numerator represent in the 20/20 notation?

In the 20/20 notation, the numerator represents the distance from the patient's eyes to the chart, typically measured in feet. This notation indicates that the patient is tested at a distance of 20 feet from the visual acuity chart. The denominator, on the other hand, indicates the smallest size of letters that the patient is able to read at that distance, which is a measure of visual acuity. This method of testing visual acuity is standard in many clinical settings and helps determine how well a person sees compared to what is considered normal vision.

Understanding this relationship is crucial for interpreting visual acuity measurements, as it informs healthcare professionals about the patient's level of sight under standardized testing conditions.