UNDER all those long lopsided fringes, a hidden danger is lurking.

A leading optometrist has warned children and teenagers are risking their eyesight for the sake of fashion.

Favoured by celebrities including Reece Mastin and Justin Bieber, the current zeal for haircuts with fringes that flop over one eye could result in a generation of young people with lazy eyes.

Optometrists Association national executive member Andrew Hogan warned amblyopia - the medical term for lazy eye - could result from obstructed vision caused by hair.

"If a young emo chap has a fringe covering one eye all the time, that eye won't see a lot of detail," Mr Hogan said.

"And if it happens from a young age, that eye can become amblyotic."

Mr Hogan said the most vulnerable age for visual development was birth to seven years, but research had shown vision could still be affected at later stages.

As well as the potential damage to eyesight, there are also concerns that long "emo" sweep fringes could cause postural problems.

Veteran hairdresser Roseanne Anderson fears the hairstyle forced many to tilt their heads to one side in order to see out of their small window of vision.

"I have to wonder how they don't get a stiff neck," the Hobart-based hairdresser said.

"I have seen lots of fashions come and go - but really when I think about it, this is probably the only hairstyle in my 40 years of hairdressing that could be a health hazard."

Mr Hogan said a curtain of hair over one eye could actually act like an eyepatch, limiting the eye's access to both sunlight and sensory stimulation.

He said recent research had shown a lack of direct sunlight resulted in short sightedness.

And hair constantly hanging over one eye could result in sensory deprivation that could weaken one eye and lead to amblyopia.

"If you walk around with an eye patch on all day, then that eye will end up seeing more poorly than the other eye," he added.

Amblyopia occurs when the nerve pathway from one eye to the brain does not develop because the abnormal eye sends a blurred image to the brain.