Final answer:
The Snellen chart was developed by Dutch ophthalmologist Herman Snellen in 1862 to measure visual acuity, featuring lines of letters in decreasing size to be read at a distance of 20 feet.
Step-by-step explanation:
The Snellen chart is named after the Dutch ophthalmologist Herman Snellen, who developed the chart in 1862. It is a standardized tool for measuring visual acuity. The Snellen chart presents a series of letters in decreasing size, which are to be read from a distance of 20 feet. A person with normal vision is expected to read the line of letters that subtend 5 minutes of an arc at this distance. Larger letters are used to approximate the visual acuity at other distances, such as 20/200 vision, indicating what a person with normal vision can read from 200 feet away.