More than one in ten people has a visual impairment that means they can't see 3D films properly, according to a British eyecare charity.
The Eyecare Trust says its been seeing an increasing number of people who complain that they can't perceive 3D images.
And the reason, it says, is that 12 percent of people suffer from a minor impairment that means their brains can't correctly process the individual images that are transmitted to them via the left and right eyes.
"This leads to an inconsistency in viewing the three spatial dimensions (height, width and depth) required to enjoy 3-D films in all their glory," it says.
If left untreated, binocular disorders such as amblyopia can affect peoples' ability to read well, and cause a greater propensity to screen fatigue when working at a VDU or watching TV for long periods of time.
And while these disorders can be easily detected in an eye test, many sufferers are not aware that they have them, as the brain can often compensate for the visual inadequacy in day to day life.
Sufferers will find that they may experience headaches and visual discomfort when watching 3D movies. Glasses or visual therapy may help.
The report is bad news for manufacturers, who are already twitchy about the health effects of 3D. Samsung recently issued a health warning about its 3D televisions, saying they could cause everything from headaches to epileptic fits and strokes.