All Blacks loose forward Ardie Savea will become the first player to wear goggles at a Rugby World Cup as he battles vision problems that have left him fearful of going blind.
The bruising back-rower, a key player for the defending champions, was not known to have had sight problems but he said the vision in his left eye was blurred and deteriorating.
Against Canada on Wednesday, Savea will wear goggles which were approved by World Rugby earlier this year to allow people who are visually impaired to play the game.
"A couple of years ago I realised I had bad vision in my left eye. Everything's kind of blurry," he said. "I told All Blacks doctor Tony Page that it was getting worse and now we're doing something about it.
"Doc notified me that World Rugby had some goggles that were approved and everyone has been really supportive. In terms of vision and seeing, it's pretty sweet, and it's now just a matter of getting used to them."
The goggles are designed to be safe for both the wearer and those coming into contact with him. Italy's Ian McKinley, who is blind in one eye, was the first player to wear them at international level.
Savea said it was an easy decision to make when he realised that he could potentially lose his sight if his other eye was damaged.
"Obviously if this right eye goes then I'm maybe, potentially blind," Savea said. "I've got my little girl and hopefully future kids and a bigger family, so I want to be able to see.
"I'm just thinking of the bigger picture and trying to protect my eyes."
All Blacks assistant coach Ian Foster said Savea did not wear contact lenses and that the goggles were purely for protection, not as a vision aid.
When asked why the All Blacks and Savea had waited until the World Cup to trial the goggles, Foster said: "This is the right time.
"When a player comes and says he felt his eye was getting worse ... it's a very natural time."
However, the revelation that Savea had vision problems was news to his All Blacks and Wellington Hurricanes teammate Beauden Barrett.
"It sort of makes sense," Barrett said. "I've never thought of it until this point but I remember trainings and games and seeing him blinking a bit more than usual."
Vannes scrum-half Florian Cazenave has also worn the goggles playing in Italy and France. Page said Savea had worn them at training and they hadn't affected his ability to play.
"It's probably been the most challenging conditions that you can get [to test them]. Humidity at up to 90 per cent, 20 degrees or so, and hard All Blacks training, and he's done pretty well," Page said.
"It's great to see someone like Ardie putting them on and being proud of it."