As Cuba faced a devastating economic crisis in the early 1990s, leading to severe food shortages and malnutritiion, some 50,000 Cubans were inexplicably struck down with sight loss. But health officials on the communist-led island as well as experts at WHO initially believed it was caused by a viral infection spreading through the population. Despite hostile relations between his country and Cuba, the American eye specialist Dr Alfredo Sadun was asked to go to the island in May 1993 to investigate. He tells Mike Lanchin about his meetings with Fidel Castro, and how he helped solve the mystery of what was termed the Cuban epidemic of optic neuropathy.

Photo: A doctor examines a patient affected by sight loss at a clinic in Havana, Cuba, May 1993 (ADALBERTO ROQUE/AFP via Getty Images)