The nurse asked the client to read the Snellen chart. Which of the following is tested?

Appeared in: Haryana CHO -2023

Explanation

The Snellen chart is the standard clinical tool for assessing distance visual acuity.
Visual acuity is the primary sensory function of the Optic nerve (Cranial Nerve II).
The test involves reading letters of decreasing size from a specified distance (usually 20 feet or 6 meters).
Therefore, asking a client to read a Snellen chart is a direct and specific test for the integrity of the Optic nerve.

Option B: The Olfactory nerve (CN I) is responsible for the sense of smell.
Option C: The Oculomotor nerve (CN III) controls most eye movements, pupil constriction, and eyelid elevation. It does not process visual information.
Option D: The Trigeminal nerve (CN V) has both sensory and motor functions for the face, including sensation and chewing.

Clinical Relevance

Nursing practice connection: Use the key finding related to Cranial Nerve II (Optic) Assessment to guide bedside assessment, documentation, and the next nursing action.
Routine vision screening is a fundamental part of a comprehensive neurological exam and general health assessment.
A sudden or progressive decline in visual acuity can be an early sign of serious underlying conditions, such as optic neuritis (often associated with multiple sclerosis), glaucoma, cataracts, or brain tumors compressing the optic pathway.
What if? If a patient cannot read even the largest letter on the Snellen chart at 20 feet, the nurse should move the patient closer or switch to testing for the ability to count fingers, detect hand motion, and finally, perceive light. This helps quantify the degree of severe vision impairment.

How to Approach the Question

First, identify the key procedure mentioned in the question stem: 'read the Snellen chart'.
Recall the purpose of this specific clinical test. The Snellen chart is exclusively used to measure distance visual acuity.
Next, connect this function (vision) to the corresponding anatomical structure. Ask yourself, 'Which cranial nerve is responsible for the sense of sight?'
Review the functions of the cranial nerves listed in the options: Optic (vision), Olfactory (smell), Oculomotor (eye movement), and Trigeminal (facial sensation/chewing).
Based on this, conclude that testing visual acuity with a Snellen chart directly assesses the Optic nerve.

Concept Tested & Keywords

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E6 Medicine Harrison 22e Part 2 p. 1284-1286

E6 Medicine Macleod Clinical Examination 15e p. 150-152

Practise the full Haryana CHO -2023

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