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Films such as Maleficent and The Lego Movie may be made to be watched in 3D on a cinema screen, but a French agency claims that such films could damage children's eyesight.

ANSES, France's national health and safety agency, has called for a ban on stereoscopic technology such as 3D films and games for children under the age of six, while it recommends that children below the age of 13 should only use the technology occasionally.

However, one vision expert claims there is little evidence to back up a ban, as only short-term discomfort has been recorded in children and adults watching 3D films.

The French health and safety executive, ANSES, has called for ban on stereoscopic technology such as 3D films (a still from Disney's Maleficent which was shown in 3D is pictured) and games for children under the age of six, while it recommends that children below the age of 13  should only watch the occasionally

ANSES, the country's National Health Security Agency for Food, Environment and Work, published a research paper claiming that a ban should be considered because of 'the possible [negative] effect of 3D viewing on the developing visual system.'

The human vision system changes 'significantly' during infancy, including parts of the brain that perceive depth, associated with 3D films, according to an article by Martin Banks, Professor of vision science at the University of California at Berkeley, published in New Scientist. 

Changes occur until the teenage years and the visual experiences a child receives, affects the development of binocular circuits, which are needed for depth perception.

'These observations mean that there should be careful monitoring of how the new technology affects young children,' he warned. 

He writes that two properties of binocular vision - vergence and accommodation – which can come into conflict when watching 3D films to produce a feeling of discomfort, seem to be troubling the French experts.

In everyday life, our eyes move from one object to another. When the eyes are focused on an object, vergence is 'acute' and the viewer sees a single object, not two.

 ANSES' research paper says a ban should be considered because of 'the possible [negative] effect of 3D viewing on the developing visual system,' whereas a vision expert claims that there is no evidence to suggest long-term damage from watching 3D films (illustrated with a stock picture)

To get a single, sharp image, the eyes are focused to produce a clear image on the retina, while an image is focused by changing the curvature of the lens within each eye, which is known as 'accommodation'.

Usually, both properties of binocular vision are operating on one object placed a certain distance away from the eye, but in 3D films, the image appears in front or behind the screen. 

The difference in distance means that there can be a conflict, which makes images appear blurry to some people. This blurriness has been proven to cause some people discomfort.

However, Professor Banks says there is no existing evidence to prove that adverse effects from watching 3D films cause permanent damage to humans' eyesight.

'On that basis.it seems rash to recommend these age-related bans and restrictions,' he said.

He acknowledges that there are always health risks with the widespread roll out of new technology, but there is 'no smoking gun to suggest harm is being caused,' adding that a ban on 3D films for children seems 'unnecessarily harsh'.