Research Agenda for Global Blindness Prevention:

Clinical Conditions: 4. Xerophthalmia

Research opportunities

• Short- to Medium-Term
  
  
• Medium-Term
  
  
• Medium- to Long-Term

Xerophthalmia was traditionally a major cause of visual disability among young children, particularly in South and Southeast Asia and in Africa.

Recent studies confirm it is also prevalent, primarily as night blindness, among women of reproductive age.

The discovery that vitamin A deficiency (VAD), the cause of xerophthalmia, is far more prevalent than clinically evident ocular complications, and that mild levels of deficiency dramatically increases infectious morbidity and mortality, have resulted in global initiatives (UNICEF, WHO, USAID) to control micronutrient malnutrition.

As a result, over 70 countries have launched VAD control programs. UNICEF estimates these reach 80% of their target childhood populations in over 40 countries.

As a result, many countries have witnessed a dramatic decline in the incidence of xerophthalmia and related blindness (formal assessment in Indonesia suggests a 92% reduction in the prevalence of active disease).

The primary constraint to VAD control is a cost-effective method for improving vitamin A status. We now know that one cannot normalize vitamin A status by simply changing dietary habits of populations dependent upon a vegetable diet, because the bioavailability of vitamin A from carotene-containing fruits and vegetables is much lower than previously thought.

Fortification of dietary staples would provide a cost-effective means of supplementing diets with additional vitamin A.

Unfortunately, few centrally processed products, in which vitamin A is stable, are consumed by high risk populations. Identification of such potential vehicles for fortification remains a high priority.

The single most important intervention strategy remains periodic administration of high-dose supplements (generally once every 3-6 months). The supplements themselves are extremely inexpensive, but distributing them is not.

Many countries have successfully grafted vitamin A distribution onto NIDs ("National Immunization Days") utilized to eradicate polio through mass immunization.

As many countries have successfully eradicated polio, NIDs are being phased out and alternative delivery schemes need to be adopted.

Increasingly, other micronutrient deficiencies are being recognized as important targets for control, and wherever possible, combined with vitamin A supplementation. But there is little data on the potential interactions between co-administered multiple micronutrients.

Short- to Medium-Term:

• Develop better tools for population assessment of vitamin A status

Medium-Term:

• Develop and test alternative supplementation strategies (e.g., use of market forces to propel and sustain programs)
  
  
• Generate additional information on the role of vitamin A status in determining maternal mortality, and the impact of control of VAD
  
  
• Conduct population-based trials to elucidate

  micronutrient-micronutrient interaction, and to establish appropriate supplementation and fortification strategies for populations with different degrees/states of micronutrient deficiency

Medium- to Long-Term:

• Determine the impact of very early (birth) vitamin A supplementation on the developing immune system, as this may have enormous consequences for morbidity and mortality, and thus for the justification of vitamin A control programs
  
  
• Develop, refine and evaluate the value of crops bio-engineered to produce beta-carotene and/or retinol

Next: 5. The Glaucomas

Also see: Table of Contents of the Research Agenda for Global Blindness Prevention