Final answer:
Vitamin A deficiency is the leading cause of blindness in children under 5 in West and Central Africa, impacting the immune system and causing visual impairment.
Step-by-step explanation:
The leading cause of blindness in children under the age of 5 in West and Central Africa is due to vitamin A deficiency. Vitamin A is crucial for proper immune system function and visual health and its deficiency can result in impaired vision and even total blindness in severe cases. In developing regions where malnutrition is prevalent lack of this essential nutrient is a significant health concern contributing to a high incidence of preventable blindness among young children. While cataracts are typically age-related and are often attributed to repeated exposure to UV-B rays, they are collectively topped by vitamin A deficiency-related conditions for vision impairment in the mentioned demographic. Proper nutrition, including adequate intake of vitamin A, is paramount in preventing such consequences in these vulnerable populations.