Night blindness is caused by which vitamin deficiency?

Appeared in: NORCET 3 - 2022 (Shift-1)

Explanation

Vitamin A (retinol) is an essential precursor for 11-cis-retinal, a molecule required for vision.
11-cis-retinal combines with the protein opsin to form rhodopsin, the light-sensitive pigment in the retina's rod cells.
Rod cells are responsible for vision in low-light conditions.
A deficiency of Vitamin A impairs the regeneration of rhodopsin after exposure to light, causing delayed dark adaptation, which manifests as night blindness (nyctalopia).
Night blindness is recognized as the earliest clinical sign of Vitamin A deficiency.

Option B: Vitamin D deficiency is primarily related to bone health, not vision.
Option C: Vitamin E deficiency is rare and primarily affects the nervous system and red blood cells.
Option D: Vitamin K is essential for blood coagulation, not for vision.

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Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Vitamin deficiencies and their clinical manifestations as background academic context rather than a clinical decision trigger.
Night blindness is an early and reversible sign of Vitamin A deficiency. Nurses should assess for this symptom, especially in at-risk populations like young children and pregnant women in undernourished settings, to allow for timely intervention.
Patient education is a key nursing role. This includes advising on dietary sources of Vitamin A (e.g., green leafy vegetables, yellow fruits, liver, eggs) to prevent deficiency.
What if? If a child presents with Bitot's spots in addition to night blindness, it signifies a more severe and chronic deficiency (xerophthalmia). The nursing priority shifts from dietary advice to ensuring urgent administration of high-dose Vitamin A supplements as prescribed, to prevent irreversible corneal damage and blindness.

How to Approach the Question

This is a direct factual recall question from the topic of nutrition and vitamins.
First, identify the key term in the question: 'Night blindness'.
Recall the specific functions of the fat-soluble vitamins listed in the options (A, D, E, K).
Connect 'night blindness' to the vitamin responsible for vision, specifically vision in dim light. This is Vitamin A, which is a component of the retinal pigment rhodopsin.
Eliminate the other options by recalling their primary functions: Vitamin D for bones, Vitamin E as an antioxidant, and Vitamin K for blood clotting.

Concept Tested & Keywords

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Practise the full NORCET 3 - 2022 (Shift-1)

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