Six Million Brits suffer from poor binocular vision - which gives them headaches and achey eyes when watching 3D films.

So says The Eyecare Trust, which tells us that 3D relies on our eyes's abilities to work as a "co-ordinated team to achieve an accurate perception of depth".

But if you have poor binocular vision, your brain cannot correctly process individual images aimed at left and right eyes. And that makes everything blurry when watching a 3D film - or it makes your brain work overtime to "compensate for any visual inadequacies"

Which means that you might not know that you suffer from poor binocular vision. An eyetest and new eyeglasses will soon sort you out.