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MBBS QUESTION #10280
Question 1
A patient reports difficulty seeing in dim light (night blindness) while daytime vision remains normal. This is most consistent with a problem affecting which retinal pathway, often related to vitamin A deficiency?
  • Cone-mediated (photopic) vision
  • Rod-mediated (scotopic) vision✔️
  • Optic nerve conduction, affecting both rods and cones equally
  • The lens's accommodative mechanism
Correct Answer Explanation
Rods, which mediate vision in dim light (scotopic vision) and depend on the vitamin A derivative retinal for the visual pigment rhodopsin, are selectively affected in vitamin A deficiency and certain retinal dystrophies, producing isolated night blindness while cone-mediated (daytime, color) vision remains relatively preserved.