Blindness in the tropics.

Blindness is a major problem in most developing countries. It occurs at ten times the rate seen in the developed countries and in over 80% of cases is either preventable or curable. The four main causes are cataract, trachoma, onchocerciasis and xerophthalmia. Cataract, which is responsible for half the blindness, can be effectively cured with modern cataract surgery. Trachomatous blindness follows frequent episodes of reinfection, which can be prevented by simple hygienic measures. Onchocerciasis can be halted by the simple administration of a once-a-year dose of ivermectin, a drug which is currently being provided at no cost to all those with this infection. Vitamin A deficiency, which causes xerophthalmia, can be prevented by vitamin A distribution programs or dietary education. The challenge is to deliver these interventions effectively in the areas of need.