New Zealand flanker Ardie Savea will wear protective goggles in Wednesday's World Cup match against Canada following fears he could go blind.

Savea, 25, revealed the sight in his left eye has been deteriorating and he will now wear specially-designed glasses to protect his right eye.

If he comes off the bench against Canada he will become the first player to wear goggles in a World Cup match.

"Obviously if my right eye goes, I might be potentially blind," he 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.

"In terms of vision and seeing [with the goggles], it's pretty sweet, and it's now just a matter of getting used to them."

Following trials, World Rugby approved the use of goggles in May.

Italy fly-half Ian McKinley, who lost the sight in one eye after an accidental boot to the face, became the first player to wear the equipment in a Test earlier this year.

Savea, who has played 40 Tests, is one of two-time defending champions New Zealand's key players, but has been left out of the starting line-up to face Canada as coach Steve Hansen rotates his squad.

"A couple of years ago I realised I had bad vision in my left eye," he said. "Everything's kind of blurry.

"I told All Blacks doctor Tony Page it was getting worse and now we're doing something about it."

Assistant coach Ian Foster said the All Blacks have been monitoring Savea's eyesight for two years and have no long-term concerns about its deterioration.

"It looks a little bit different but it's not unique," Foster said.

"I think it's great Ardie has been willing to make a decision for his health and that he's going to follow through with it."