02/12/2014 12:20 GMT | Updated 20/05/2015 10:12 BST

Can 3D Movies Harm Children's Eyesight?

Girl wearing 3D glasses

3D movies could damage children's eyesight, French health and safety experts have warned.

ANSES - French Agency for Food, Environmental and Occupational Health & Safety - says children under the age of six should be banned from watching 3D films and children under 13 should only watch them occasionally.

Children's favourites such as Maleficent, The LEGO Movie and Cloudy with a Chance of Meatballs all gave kids the option to watch in 3D, otherwise known as stereoscopic.

ANSES 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'.

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.

Writing in New Scientist, Martin Banks, Professor of vision science at the University of California at Berkeley, said the human vision system changes 'significantly' during infancy, including parts of the brain that perceive depth, associated with 3D films.

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.

He warned: "These observations mean that there should be careful monitoring of how the new technology affects young children."

He said two properties of binocular vision - vergence and accommodation – can come into conflict when watching 3D films to produce a feeling of discomfort.

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.

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.

He said: "On that basis, it seems rash to recommend these age-related bans and restrictions."

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