If the patient's best efforts allow him or her to read a 20/400 Snellen letter at a distance of 5 ft, the actual distance vision recording should be:

• A. 20/400
• B. 5/400
• C. 5/20
• D. 20/20

Answer: (B)

Understanding visual acuity notation helps interpret how far vision is tested and how it compares to normal. In Snellen notation, the first number is how far the patient was able to read the line, and the second number is how far a person with normal vision would need to be to read the same line.

If the patient can read a line that a normal eye would require being at 400 feet to read, but the patient can do it from 5 feet, the recording becomes 5/400. In other words, the tested distance is 5 feet, while the normal reference distance for that line is 400 feet, so the actual distance vision is 5/400. This indicates markedly reduced acuity.

The other common interpretations would either imply a different tested distance or a different normal-distance reference for that line, which doesn’t match the described scenario.