Visual acuity is checked by which chart?

Appeared in: Bihar CHO -2019

Explanation

The Snellen chart is the standard tool for measuring distance visual acuity.
It assesses central vision by requiring the patient to read rows of standardized letters (optotypes) that get progressively smaller.
The test is typically conducted from a distance of 20 feet (or 6 meters).
A result of 20/20 is considered normal vision, indicating the patient can clearly see at 20 feet what a person with normal vision can see at that distance.

Option A: The Ishihara chart is not used for testing visual acuity. Its purpose is to screen for color vision deficiency, particularly red-green color blindness.
Option C: This option is incorrect because the two charts serve different functions. The Snellen chart tests acuity, while the Ishihara chart tests color vision. They are not used interchangeably or together for acuity testing.
Option D: This option is incorrect because a specific, standard tool for measuring visual acuity exists and is listed as an option.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Assessment of visual acuity as background academic context rather than a clinical decision trigger.
Nurses perform visual acuity screening as part of routine health assessments, admission processes, and pre-operative checks to establish a baseline and identify deficits.
Identifying poor visual acuity is crucial for patient safety, as it can increase the risk of falls, medication errors, and difficulty with activities of daily living.
A significant finding on a Snellen test (e.g., vision worse than 20/40) warrants a referral to an optometrist or ophthalmologist for a comprehensive eye examination.

How to Approach the Question

First, identify the key term in the question: 'Visual acuity'. This refers to the sharpness or clarity of vision.
Next, recall the standard clinical tools used for eye examinations.
Evaluate each option based on its specific function. Ask yourself, 'What is the Ishihara chart for?' and 'What is the Snellen chart for?'.
The Snellen chart is specifically designed with rows of letters to test distance vision (acuity).
The Ishihara chart uses colored plates to test for color blindness.
Based on this differentiation, eliminate the incorrect options. Since the Ishihara chart is for color vision, options A and C are incorrect. Since the Snellen chart is the correct tool, option D is also incorrect.

Concept Tested & Keywords

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E6 Nursing Fundamentals Potter Perry 12e Part 3 p. 78-80

E6 Nursing Brunner Adult Health 3SA Vol 2 Part 1 p. 85-87

E6 Nelson Textbook of Pediatrics(2024) — Volume 2 p. 1716-1718

Practise the full Bihar CHO -2019

Attempt every question from this paper in a timed mock, then review the full solution for each one.