Google has warned its Glass wearable computer could result in eye strain and headaches - and has banned children from wearing the gadget amid fears it could damage their eyesight.
The search giant also advises people who have had laser eye surgery to check with their doctors.
The warnings come amid growing concern over the safety of looking at the tiny screen all day.
'Glass isn’t for everyone,' the firm says on a web site for the gadget, which is currently only available to a handful of developers.
'Like when wearing glasses, some people may feel eye strain or get a headache.
'If you’ve had Lasik surgery, ask your doctor about risks of eye impact damage before using Glass. Don’t let children under 13 use Glass as it could harm developing vision.'
Google has also banned those under 13 from connecting Glass to their account.
It also revealed customers who struggle with health issues will be given a refund.
'If Glass is not for you and you wish to return it, do so before the end of the applicable refund period,' it said.