The Swiss ski federation said Feuz was diagnosed with nerve trouble on the right side of his face at the University of Colorado hospital in Denver.
He was in Colorado to train for the World Cup season. Speed events in the men's World Cup begin with a downhill and a Super-G on November 26th-27th in Lake Louise, Canada before the circuit shifts to Beaver Creek, Colorado.
That's where Feuz took world downhill bronze in 2015. He had top-five finishes in six successive downhills last season, including a win at St. Moritz, where he also won a super-G. The Swiss venue will host the 2017 World Championships in February.
Feuz has seven career World Cup victories and finished second in the overall standings in the 2011-12 season.
The Swiss team said Feuz, 29, experienced similar symptoms as a teenager.
“As in many cases, the cause has not been identified so far, but as the optic nerve is concerned, Beat cannot compete at the moment,” the team said.
“It is not yet possible to say with certainty how long it will last.”