Bob Costas took Tuesday night off from hosting NBC's prime-time Winter Olympics coverage because of an ongoing eye ailment, ending a streak of 157 consecutive nights on which he hosted the network's Olympic show. He was replaced by "Today" show host Matt Lauer.

It was not clear Tuesday whether Costas would be able to return to work on Wednesday night's show. NBC listed him as "day-to-day" on its "injury report."

"As a practical matter, I simply couldn't do my job because my eyes had become so blurry, watery and sensitive to light," Costas said in a news release. "I'm hopeful the symptoms will improve in the next couple of days and I can return to the broadcast. Also, the last thing I want is to go through the rest of my life owing Matt Lauer a bunch of favors."

NBC said it was the first time since CBS showed the 1998 Olympics in Nagano that someone other than Costas hosted a prime-time Olympic show, and that it was the first time since 1988 someone other than Costas did so on NBC.

"I saw Bob in the hotel [Tuesday] morning, and if ever there was a guy who looked like he needed a night off, it was him," Lauer said. "I'm happy to keep his chair warm. Although I might Purell it before I sit in it!"

Costas has been wearing glasses rather than contact lenses as he battles conjunctivitis that started in one eye and spread to both. The only cure for the ailment is time; there is little of that to spare during the two-week Olympic stage that is so important to NBC every other year.

More Olympics