Title: Xerophthalmia and Vitamin A

Key words: blindness, malnutrition, supplementation, secondary Vit A deficiency, retinol-binding protein,

Date: Oct 1998

Category: 13. Specific Conditions

Type: Article

Author: Dr Van Rhijn

Xerophthalmia and Vitamin A

Xerophthalmia unresponsive to vitamin A supplementation

Introduction

Xerophthalmia (dryness of the conjunctiva and cornea) is a major cause of blindness in children in Africa, Asia and Latin America. It is associated with vitamin A deficiency and malnutrition in general and, in the presence of adequate dietary intake of vitamin A, is referred to as secondary deficiency. Several mechanisms which have been described are listed below:

Secondary causes of Vitamin A deficiency

Infection: Giardiasis; Ascariasis; Sprue

Drugs: Cortisone; Iron; Caffeine; Antibiotics

  • Zinc deficiency reduces formation of RBP
  • Protein-energy malnutrition

Vitamin A is transported from liver stores to tissues by plasma retinol-binding protein, which is synthesised by the liver. Synthesis is severely affected by conditions that cause protein-energy malnutrition, such as marasmus and kwashiorkor. It is quite common, in these conditions, to have functional vitamin A deficiency despite adequate supplementation, because here the problem is one of transport and utilisation rather than lack of supply of vitamin A. The digestion and absorption of vitamin A is also closely associated with lipid absorption.

 

Conclusion

Vitamin A deficiency is the most important preventable cause of blindness, and it is crucial to consider other factors that may contribute to vitamin A deficiency. Supplementing the diet with vitamin A alone, without correcting protein-energy malnutrition, for example, is ineffective and a waste of resources.