A patient reports difficulty seeing clearly at night despite adequate vitamin A intake. Which mechanism explains why their rod photoreceptors might still be impaired?

💡 Explanation

Impaired retinaldehyde regeneration causes night blindness because retinaldehyde, derived from vitamin A, must be continually regenerated to combine with opsin to form rhodopsin. Therefore, even with sufficient vitamin A, a dysfunctional regeneration cycle hinders vision rather than enhanced enzyme activity or synthesis.

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