While in Africa, Ridley led important research[10] into onchocerciasis when he was stationed in the Gold Coast, now Ghana, for part of his war service. In 1941 while he acted as part-time sanitation officer at the capital city of Accra, he met Brigadier G. M. Findlay, AMS, who stimulated Ridley's interest to study River Blindness, an endemic disease in parts of the country. To find onchocerciasis patients, Ridley left the coastal city and travelled overland with Captain John Holden to north west Ghana.