Final answer:
A measurement of 20/200 visual acuity means that what a person can see at 200 feet, someone with 20/200 vision must be only 20 feet away to see. It is considered the threshold for legal blindness in the United States.
Step-by-step explanation:
On the visual acuity eye chart, a measurement of 20/200 indicates that what a person with normal vision can see clearly at 200 feet, someone with 20/200 vision must stand 20 feet from the chart to see the same line of letters. This level of visual acuity is often considered the threshold for being legally blind in the United States.
The Snellen chart presents letters that decrease in size line by line. To assess vision, a person reads the letters on the chart starting from the top and going down to the smallest line they can see clearly. If the smallest line they can see from 20 feet away is the 20/200 line, their visual acuity is 20/200.