Which cranial nerve is assessed by using the Snellen visual acuity chart?
Abducens cranial nerve (CN V).
Optic cranial nerve (CN I).
Trochlear cranial nerve (CN VI).
Oculomotor cranial nerve (CN II).
The Correct Answer is D
Choice A rationale
The abducens cranial nerve (CN VI) controls the lateral rectus muscle of the eye, which is responsible for outward movement. It is not assessed using the Snellen visual acuity chart. The function of this nerve is tested through the evaluation of lateral eye movements.
Choice B rationale
The optic cranial nerve (CN II) is responsible for vision, including visual acuity and visual fields. It is assessed using the Snellen visual acuity chart to determine how well a person can see at various distances. This test evaluates the clarity and sharpness of vision, making CN II the correct answer.
Choice C rationale
The trochlear cranial nerve (CN IV) controls the superior oblique muscle, which helps with downward and inward eye movements. It is not assessed using the Snellen visual acuity chart but rather through the evaluation of eye movements and alignment.
Choice D rationale
The oculomotor cranial nerve (CN III) controls most of the eye's movements, including those of the superior, inferior, and medial rectus muscles, as well as the inferior oblique muscle. It is also responsible for controlling the pupil's response to light. The Snellen visual acuity chart does not assess the function of CN III, as it focuses on visual clarity and acuity.
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Naxlex Comprehensive Predictor Exams
Related Questions
Correct Answer is C
Explanation
Choice A rationale
The optic nerve (CN II) is responsible for vision. It transmits visual information from the retina to the brain. Dysfunction in this nerve typically results in visual disturbances such as loss of vision, visual field defects, or difficulty in distinguishing colors. It does not control the movement or strength of the tongue.
Choice B rationale
The abducens nerve (CN VI) innervates the lateral rectus muscle of the eye, which is responsible for abducting the eye (moving it outward). Dysfunction in this nerve can lead to strabismus (misalignment of the eyes), double vision, or inability to move the eye outward. It does not affect tongue movement or strength.
Choice C rationale
The hypoglossal nerve (CN XII) innervates the muscles of the tongue, controlling its movement and strength. Dysfunction in this nerve can result in difficulty protruding the tongue, poor strength against resistance, and impaired speech or swallowing. Therefore, the symptoms described in the question indicate a dysfunction of the hypoglossal nerve.
Choice D rationale
The vestibulocochlear nerve (CN VIII) is responsible for hearing and balance. It transmits sound and equilibrium information from the inner ear to the brain. Dysfunction in this nerve can lead to hearing loss, tinnitus, vertigo, or balance problems. It does not control tongue movement or strength.
Correct Answer is D
Explanation
Choice A rationale
Myopia, or nearsightedness, is when distant objects appear blurry because light rays focus in front of the retina. A Snellen exam result of 20/50 means the client can see at 20 feet what someone with normal vision sees at 50 feet, indicating reduced distance vision. However, this condition does not correlate with the ability to read the Rosenbaum chart, which is for near vision, thus excluding myopia.
Choice B rationale
Normal vision is not indicated by a Snellen exam result of 20/50, as this signifies a visual impairment where the client sees at 20 feet what a person with normal vision sees at 50 feet. Normal vision would be indicated by 20/20 on the Snellen exam.
Choice C rationale
Presbyopia is the age-related loss of the eye's ability to focus on near objects, typically noticeable in people over 40. Although this condition involves difficulty reading at close range, the client's uncorrected Snellen exam result of 20/50 pertains to distance vision, which differentiates presbyopia from the given scenario.
Choice D rationale
Hyperopia, or farsightedness, is when close objects appear blurry because light rays focus behind the retina. The client's ability to read the Rosenbaum chart without difficulty indicates good near vision, while the Snellen exam result of 20/50 reflects reduced distance vision, thus supporting the diagnosis of hyperopia.
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