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Physiology · Special senses: amblyopia
Sample itemA 9-year-old child has a dense unilateral congenital cataract present since birth, removed only now. Despite a clear lens and a good prescription, vision in that eye stays poor. What is the mechanism?
Original practice item, not a recalled exam question. Nothing here is recorded.
The answer and the reasoning
D. Cortical deprivation during a critical period
In early childhood, the visual cortex needs balanced input from both eyes. Deprivation of one eye allows the other eye's inputs to take over ocular dominance columns, causing amblyopia that is hard to reverse after the critical period.
Option by option
A. Permanent photoreceptor loss from lack of light
The retina is generally intact, and the deficit lies mainly in the cortex.
B. A refractive error that glasses cannot fix
A clear lens and correct prescription exclude uncorrected refractive error.
C. Optic nerve regrowth after surgery
Optic nerve regrowth is not part of this condition.
D. Cortical deprivation during a critical period (correct)
Correct. Cortical development depends on early input, so a deprived eye loses cortical representation.
Source note: Original NextPrep sample item — pending expert review. This item is original practice material awaiting independent expert review, so confirm important facts in a standard textbook.
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