NHA Certified Clinical Medical Assistant (CCMA)Clinical Patient CareEasy
A medical assistant is performing a visual acuity test using a Snellen chart. The patient reads the 20/40 line with their right eye. Which of the following statements accurately describes this finding?
- AThe patient can see at 40 feet what a person with normal vision can see at 20 feet.
- BThe patient has impaired near vision in the right eye.
- CThe patient can see at 20 feet what a person with normal vision can see at 40 feet.
- DThe patient has excellent distance vision in the right eye.
Show answer & explanationAnswer & explanation
Correct answer: C. The patient can see at 20 feet what a person with normal vision can see at 40 feet.
A Snellen chart reading of 20/40 means that the patient can see at 20 feet what a person with normal (20/20) vision can see at 40 feet. The first number is the distance the patient stands from the chart, and the second number is the distance at which a person with normal vision can read that line.
Why the other options are wrong
- A. This statement reverses the meaning; the patient sees at 20 feet what normal vision sees at 40 feet.
- B. The Snellen chart tests distance vision, not near vision.
- D. 20/40 vision indicates reduced, not excellent, distance vision.
Snellen Chart Interpretation
Understanding the meaning of the fractional numbers obtained from a Snellen eye chart test for distance visual acuity.
- First number: distance patient stands from chart (usually 20 feet).
- Second number: distance at which a person with normal vision can read the same line.
- 20/20 is normal vision.
- Higher second number indicates poorer vision.
Memory trick: Snellen: See Near, Not Far!