(CNN) -- Take your thumb and hold it out directly in front of you, away from your face. Now close the left eye. Open it and close the right eye.
Your thumb appears to have moved, even though you didn't move it with your arm. Three-D technology capitalizes on this effect, taking advantage of the brain's ability to fuse two images into one. Those glasses that you have to wear when watching something in 3-D are basically helping your brain interpret two flat images as one object that has depth.
With the success of "Avatar," a cluster of 3-D movies, including "Alice in Wonderland" and "How to Train Your Dragon", are making their mark in Hollywood. Martin Scorsese recently announced plans to direct a 3-D film later this year. Nintendo also announced plans for a 3-D gaming console, the 3DS. Many electronics companies have 3-D television models, bringing the opportunity for this enhanced viewing into the home as networks begin to air more 3-D programming. Comcast's 3-D channel aired the Masters Golf Tournament earlier this month, and ESPN plans to launch a 3-D sports network this year.
But doctors say that for eyes unaccustomed to watching 3-D for hours every day, there are some dangers, including mild symptoms such as disorientation and, in rare cases, seizures.
The Samsung 3D LED TV comes with a substantial health warning. It cautions that certain flashing images or lights could induce epileptic seizure or stroke, and that "motion sickness, perceptual aftereffects, disorientation, eye strain and decreased postural stability" may result...