The Pentagon has put in an order for prototype contact lenses that give users a much wider field of vision. The lenses are designed to be paired with compact heads up display (HUD) units - glasses that allow images to be projected onto their lenses. Much bulkier HUDs are already deployed by the US Army and Air Force to superimpose data about targets and other status updates over users' views. The tech could help troops enhance their awareness on the battlefield.

The lenses work by allowing the wearer to focus on two things at once - both the information projected onto the glasses' lenses and the more distant view that can be seen through them. They do this by having two different filters.

The central part of each lens sends light from the HUD towards the middle of the pupil, while the outer part sends light from the surrounding environment to the pupil's rim.

The retina receives each image in focus, at the same time.

"Normally, for example, with a camera you focus on something distant or something close - but you focus on a particular spot," said Mr Willey.

"By wearing our contact lens you automatically have this multi-focus, or dual-focus, and you are doing something that humans don't usually do."