3D movies may cause vision fatigue

Meanwhile, Dr. Daniel Adams of UCSF explained that frequent eye movements or adjustments were responsible for causing a small number of people to experience symptoms such as motion sickness, nausea or dizziness.

"When you watch a 3-D movie, you're making [small and frequent] eye movements because the objects on the screen appear closer or farther away than they actually are," explained Adams. 

"If you obey the brain reflex and focus your eyes on the image (up close or in the distance), it goes out of focus. You have to break that reflexive loop [and] in some people, that may cause a little discomfort."