When using a Snellen alphabet chart, the nurse records the client’s vision as 20/40. Which of the following statements best describes 20/40 vision?
A. The client has alterations in near vision and is legally blind.
B. The client can see at 20 feet what the person with normal vision can see at 40 feet.
C. The client can see at 40 feet what the person with normal vision sees at 20 feet.
D. The client has a 20% decrease in acuity in one eye, and a 40% decrease in the other eye.
Correct Answer: B. The client can see at 20 feet what the person with normal vision can see at 40 feet.
The numerator refers to the client’s vision while comparing the normal vision in the denominator. The results of visual acuity are classically reported using 20/20 (6/6 when using meters) for standard vision. The numerator describes the distance from the chart, typically 20 ft (6 m). The denominator describes the distance that an individual with normal vision (20/20 vision) can read the same line on the chart.
Option A: The WHO describes individuals with low vision as having a best-corrected vision of 20/60 or worse, and blind as best corrected vision worse than 20/400, whereas legal blindness is identified as 20/200 in the United States. These formal definitions can have ramifications when it comes to accommodations and abilities to operate a motor vehicle.
Option C: Visual acuity decreases as the number increases and improves as the number decreases. Although 20/20 visual acuity has been referred to as “perfect vision,” it is important to remember that this is only one aspect of vision and does not include other elements such as depth perception, peripheral vision, and colorblindness.
Option D: Visual acuity testing is essential as many of these factors can be benefited from early intervention. It is crucial to determine an individual’s best-corrected visual acuity. The goal of the visual acuity test is to determine clarity or sharpness of vision. Visual acuity testing examines a patient’s ability to distinguish different optotypes (recognizable letters or symbols) at a standard distance.
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