Sadly, 3D glasses simply don’t work for some people. As you may know, a stereoscopic illusion can be created by feeding slightly different images into each eye, and the bigger the difference between the two images, the deeper the 3D effect. That is how 3D glasses can create such amazing effects at the movie theater.
Offsetting the left and right images through the glasses simulates what’s known as binocular disparity; this is a side-effect of the gap between your left and right eyes. Since our eyes are an inch or two apart, even when though they are focused on the same thing, our brain will receive a slightly different input from each eye. This aids your depth-perception, and it is the principle upon which 3D glasses are built, to create the stereoscopic illusion we see in movie theaters.
However, any physical condition that interferes with your binocular disparity will lessen the effect of 3D glasses in a movie theater. Disorders where one eye sends much less visual information to the brain than the other eye, such as amblyopia, will cancel out the 3D effect. In fact, amblyopia is relatively common, and since the condition is subtle, it often goes unnoticed until later in life.
Likewise, unilateral optic nerve hypoplasia and strabismus can also cause a person not to see a movie in 3D. Unilateral optic nerve hypoplasia is an underdeveloped optic nerve, and strabismus is a condition in which the eyes do not properly align.
The most surprising thing is that many people have perfectly normal vision, and still can’t see 3D through movie theater glasses. In real life, depth perception involves many factors that go well beyond binocular disparity. There are also many significant monocular depth cues, such as relative scale, motion parallax, texture gradients and aerial and linear perspective that contribute greatly to human depth perception.
Try closing one eye and look around; is your visual field somewhat compressed? Does it feel as if you are looking through a telephoto lens? Don’t worry, you won’t bump into anything, because your brain can easily compensate for not having binocular vision.
You could also easily have something like amblyopia interfering with your binocular disparity, but still have good depth-perception, simply because you are still receiving a lot of visual information from other sources pertaining to depth and distance.
While not being able to see 3D through movie glasses may be disappointing, it’s not at all uncommon. As long as your eyesight is good and your eyes are healthy, don’t worry too much about 3D glasses not working for you.