Natural history of onchocerciasis.

Since the first description of ocular onchocerciasis in Africa was published (Hissette, 1931) many records have been made of the ocular lesions (e.g. Bryant, 1935; Hissette, 1938; Toulant and Boithias, 1952a, 1952b, 1954; World Health Organization Regional Conference on Onchocerciasis, 1956). However, no detailed account has been written of the progress of ocular signs and visual acuity in an untreated community, nor has any serious attempt been made to study the prognosis of ocular lesions in onchocerciasis. The need for such assessment is indicated by recent estimates that the disease is the cause of blindness in 10,000 persons in the Northern Territories of the Gold Coast (Waddy, 1956) and 20,000 persons in Northern Nigeria (Budden, 1956) and by the discovery of increasing numbers of Europeans suffering from early ocular lesions acquired in these territories. Recently an investigation was completed in which a record was made of the changes in visual acuity which occurred during a few years in a village community. In this paper these changes are related to the age, intensity of infection, distribution of microfilariae, and changes in ocular signs. Moreover, an attempt is made to classify the patients seen in Nigeria with a view to providing some guide to prognosis and some indication of which patients require treatment to prevent serious loss of vision.