The term signifies visual acuity where an individual can see clearly at 20 feet what someone with standard eyesight can see at 30 feet. It’s a measurement of how well someone can discern details at a distance. As an example, a person with this level of sight might have slightly reduced sharpness compared to perfect vision but still be able to perform most daily activities without corrective lenses.
Possessing this level of sight is often considered acceptable for many tasks and activities, including driving in most jurisdictions. Historically, measurement of visual clarity has been crucial for various professions, such as pilots and law enforcement officers, where accurate distance perception is critical. This type of measurement helps to determine eligibility for certain roles and allows for appropriate corrective measures if needed.