When Darnyi was 15 years old, he lost the vision in his left eye as a result of being hit by an icy snowball three years earlier. He entered the 1988 Olympic Games as the world record holder in both the 200m and 400m medleys. In Seoul he won both races and set another world record in each. At the Barcelona Games in 1992, Darnyi successfully defended both of his Olympic titles and completed an eight-year stretch during which he was undefeated at either distance.