The most frequently occurring clinical indicator of vitamin A deficiency is night-blindness, which is the earliest manifestation of xerophthalmia.
In its mild form it is generally noticeable after stress from a bright light that bleaches the rhodopsin (visual purple) found in the retina. Vitamin A deficiency prolongs the time to regenerate rhodopsin, and thus delays adaptation time in dark environments.
Night-blind young children tend to stumble when going from bright to dimly-lit areas and they, as well as night-blind mothers, tend to remain inactive at dusk and at night.
