According to research published in the Journal of Vision, the devices put extra strain users' eyes.
Martin Banks, professor of optometry and vision science at the University of California in Berkeley, warned that this discomfort could lead to a limit being placed on the use of the technology.
"This is an area of research where basic science meets application and we hope that the science can proceed quickly enough to keep up with the increasingly widespread use of the technology," he said.
Meanwhile, new research has found that almost half of American smartphone owners have used their device to assist in some part of the food shopping process.
Some 34 per cent used the device in store to research food product information, while 43 per cent used their smartphone to manage a food shopping list while not in a store.
Posted by Simon Jones
