Viewing movies and television in 3D experienced a huge surge in popularity a few years ago, but the technology is nothing new. We’ve been constructing ways to see 3D images on 2D surfaces for almost two hundred years. But how exactly does a pair of goofy glasses make images jump off the silver screen?

The basics of 3D glasses

3D glasses play on our binocular vision. Binocular vision means both eyes focus on the same object, creating a sense of depth. For people with conditions that impair the binocular function of their eyes, 3D glasses may not work properly. Fortunately, most of these issues can be corrected with therapy, surgery, or even special prescription eyeglasses.

While there are three different types of 3D glasses and they all do something a little different, each works on the same basic principle: filtering the world differently for each eye. Because our eyes are binocular, separate manipulation of each eye can have the desired “3-dimensional” effect if done correctly.

Early 3D technology

Although the phenomenon of 3D movies and television being ubiquitous is placed securely in the 21st century, 3D technologies have actually been around for much longer. Early versions of 3D viewing technology from the 1800’s included looking at separate but similar photographs placed over one another. Doing so with crossed eyes gave the illusion of dimensionality. We still see some of these “magic eye” tricks around today. Yet for obvious reasons, we don’t ask film audiences to sit in the theater for two hours with their eyes crossed.

Stereoscopes came about in the late 1800’s and early 1900’s as a way to let people view 3D images without crossing their eyes. You’re probably familiar with the View-Master, which was a children’s toy that utilized stereoscope technology.

Today we have 3D glasses, and they come in three varieties: anaglyph, polarized and shutter.

Anaglyph glasses

These are the stereotypical “3D glasses” with one blue lens and one red lens. How these glasses work is by filtering out specific light colors. While one side of the glasses filters blue, or cyan, the other does red. When used in conjunction with a screen displaying a double image, the result is a 3D picture.

Polarized glasses

Most 3D glasses in use today are utilizing polarized lens technology. Polarized lenses are lenses built to filter light. You may be familiar with polarized sunglasses, which block horizontal light from reaching your eyes, thus reducing glare. Polarized 3D glasses are similar in principle. Double images are projected onto the screen, and each lens is designed to filter light from one image. Usually, one lens is filtering horizontal light and the other is filtering vertical light. Combined together, this gives the impression of a 3D image.

Don’t go thinking you can bring your sunglasses to the movie theater. Despite using the same basic technology, polarized sunglasses won’t help you see a 3D image.

That doesn’t mean you should throw out your sunglasses, though! Consistent use of UV-blocking sunglasses can keep your eyes healthy and protect them from damage. You can even order prescription sunglasses online.

Shutter glasses

Shutter glasses are the most advanced type of 3D glasses. They are battery-powered and work directly with LCD screens. Unlike passive forms of 3D glasses, shutter glasses change in real time, darkening and lightening each lens in sync with the images on the screen. The image quality with shutter glasses is much higher than polarized or anaglyph glasses, and they usually come with a heftier price tag to prove it.

Are 3D movies safe for your eyes?

Long term research into the effects of 3D movies or video games on eyesight and eye health is limited. However, of the research that does exist, there appears to be no evidence that viewing your media in 3D harms vision or overall eye health.

Minor side effects may occur with 3D. Roughly half of audiences report some level of nausea, eyestrain or headaches accompanying 3D movies. These symptoms, however, are usually very mild and can be mitigated by sitting further from the screen and remaining hydrated. If you start to feel ill or uncomfortable during a 3D experience, remove your glasses and let your eyes rest for a while.

There is also no reason to bar children from seeing 3D movies. Once a child hits age 3, their binocular vision should be completely developed. 3D glasses may not work on younger children, but there is no evidence to suggest they are harmful.

3D and prescription glasses

3D glasses can often fit over prescription glasses. If this doesn’t work well for you, consider wearing contact lenses, instead. If you have an accurate prescription, you can buy your contact lenses online. If contact lenses aren’t an option for you, then ask your local theatre if clip ons are available. Many theatres offer 3D glasses designed specifically to attach smoothly to regular eyeglasses.