How Eye Puzzles Work

eye puzzle
3-D eye puzzles like this one can be difficult -- often impossible -- for some viewers to solve. Can you see the 3-D element? No? You'll have to click to the next page to see the illusion.
Image courtesy of Fred Hsu.

Ever since James Cameron released his award-winning movie "Avatar" in 3-D, it seems everyone and everything is jumping on the 3-D wagon. Next it was more 3-D movies, then 3-D television in your home -- all with the help of not-so-stylish 3-D glasses.

But remember back in the 1990s when 3-D could be achieved without the dorky glasses? Autostereograms, or eye puzzles, saw their hay day back in the '90s with the popularity of brands like Magic Eye. You probably remember them hanging in the back of an art or poster store where there would be a crowd of people ogling a rather psychedelic looking image. The scrutinizers would either exclaim with glee that they could see a 3-D object pop out at them from the chaos or with frustration that they just couldn't make sense of the crazy image. With all this 3-D hubbub, will the 3-D illusions known as eye puzzles make a come-back? Or is it these older 3-D illusions that have influenced today's media?


The latest 3-D technology available on certain cell phones, and the new Nintendo 3DS are one step closer to eye puzzles in that they do not require the use of 3-D glasses to see the illusion. However, they don't take the work eye puzzles do to uncover the illusion. So why go through the trouble of crossing your eyes and trying to "see through" the image to solve an eye puzzle? Well, some doctors say the action of solving eye puzzles may actually be beneficial, especially to patients who suffer from depth perception issues. Others claim it can be stress relieving, since the key to solving an eye puzzle is to relax the muscles in your eyes. But healthy side effects aside, solving eye puzzles is just plain fun. Especially when you can solve them before your friends can.

To understand how the "magic" happens, we first need to understand how the eye works. To learn how 3-D vision is possible, read on to the next page.


The 3-D Illusion

eye puzzle
Did you expect to see a shark floating behind all of that color? If you had trouble seeing it, there are tips to solving these puzzles coming up.
Image courtesy of Fred Hsu.

The science of vision seems like magic in and of itself. To think a tiny little 1-inch-diameter (2.54 centimeter) organ is responsible for our being able to see the world around us -- all of its color, light and depth. To achieve this miracle of sight, light enters the eye through the cornea and makes its way to the back to the retina, located in the middle of the eye. Within the retina are a variety of rod cells and cone cells that are responsible for seeing color and detail. The retina also contains something known as visual purple, or rhodopsin for those science buffs out there. It is this chemical that takes the messages from the eye and translates them into electrical impulses for the brain to interpret [source: Bianco]. If it weren't for the brain, vision would not be possible either. In fact, it is the brain that is key to 3-D vision, not the eye.

Because we all have two eyes that are set apart, each eye takes in a slightly different view of the world. Have you ever taken your 3-D glasses off during a movie? That slightly blurred image that looks like layers of the same image that haven't quite been lined up properly is how your eyes see the world. However, once these images are turned into electrical impulses for the brain to interpret, the brain creates the illusion of depth and stereoscopic, or three-dimensional, vision.


So what does the science of vision have to do with eye puzzles? Ever since the discovery of stereoscopic vision, scientists have been trying to create the illusion of 3-D from flat objects based on the way the eyes and brain create depth in our three-dimensional world. We'll dive further into the history of 3-D vision and autostereograms on the next page.

History of Eye Puzzles

The stereoscope -- the first version of 3-D imagery -- used two images of the same object from slightly different vantage points.
Brand X Pictures/Getty Images

The phenomenon of stereoscopic vision was discovered in 1800s [source: BBC]. With that discovery came the first attempt at creating 3-D images from flat drawings -- the stereoscope. While there are different versions of a stereoscope, it is always two images of the same object from slightly different vantage points positioned side-by-side. When viewed through a lens, your brain merges them together into one 3-D image [source: NCSSM].

Attempts at 3-D illusions continued on for many years, but always used two images, much like the way your eyes see the world. With the invention of cameras, creating two, slightly different perspectives of one image became much easier. Then came the blue and red glasses 3-D effect, formally known as anaglyphs. Using a red and blue image, the glasses block out part of the image, allowing you to see two different perspectives when wearing the glasses. From this came vectographs -- the first 3-D illusion presented as a single image. However, it still required the use of special 3-D glasses.


It wasn't until 1959 when Dr. Bela Julesz created autostereograms that doctors and scientists began to believe stereoscopic vision and depth perception occurred in the brain rather than the eye. While studying images from a spy plane of camouflaged objects, Dr. Julesz discovered the random dot stereogram [source: Magic Eye 3-D]. With the help of a computer, he created an image of randomly distributed dots of uniform shape and size. His test proved his theory and also led to his student creating the first 3-D illusion that could be seen from a single image without the use of glasses or lenses.

With the help of computers, eye puzzles emerged in three different forms -- random dot, random text and texture. In 1991, Tom Baccei teamed up with artist Cheri Smith to improve the single image texture stereogram. With the help of advancing computer technology and a full-spectrum of color, the pair created the very popular brand Magic Eye [source: Magic Eye].

While autostereograms create a 3-D illusion without the use of special glasses or lenses, there are techniques one must employ in order to see the 3-D illusion. We'll learn how to see the magic on the next page.


Tips for Solving Eye Puzzles

The fun of eye puzzles is that you must "solve" them. If you don't know the right trick to uncovering the 3-D image, you could stare at the same chaotic image for years without the satisfaction of seeing the hidden 3-D image.

The key to all viewing methods is to relax your eye muscles and focus your eyes beyond the eye puzzle image. The recommended viewing technique is known as the "parallel-viewing method." It suggests the viewer attempt to look "through" the picture, focusing the eyes on an imaginary spot in the distance, behind the image. Since your eyes will naturally want to focus on the image in front of you, this technique requires concentration and is often difficult to master.


An easier, but similar method goes against everything your mother taught you as a child -- "Don't cross your eyes!" Well, if you're having trouble solving an eye puzzle, you might want to ignore your mother's warning. Looking at an eye puzzle with eyes crossed actually forces your eyes to focus on a point in front of the eye puzzle image. This is often easier for viewers than focusing behind the image. The only issue with this technique is the image will appear to sink away from you rather than pop out at you [source: 3dWonderStuff].

If you happen to be looking at a framed eye puzzle or one printed on glossy paper, you might want to try the reflection technique. With light shining on the glossy image, focus your eyes on a glare. This will achieve the same relaxation of the eye muscles to allow you to see the hidden 3-D image or message.

Another trick that works with eye puzzles with repeating images is to fix your eyes on two side-by-side images. If you focus long enough, the two images will merge into one and you'll be able to continue looking around the eye puzzle to see more 3-D.

Finally, you might want to hold the eye puzzle up to your nose. This will force your eyes to relax, because you will not be able to focus on the image. Slowly move the eye puzzle away from your face, while keeping your eye muscles relaxed and unfocused. Another trick is to put your finger halfway between the eye puzzle and your face. Slowly move your finger closer to your face. In the same way, this causes your eyes to lose focus and the hidden 3-D message to be revealed [source: Inglis].

Have you tried all of the suggested viewing methods without any luck? Read on to the next page to find out what it means if you can't solve an eye puzzle.


What if I can't see it?

While solving eye puzzles makes most viewers giddy with delight, if you're having trouble seeing the 3-D image, eye puzzles can be insanely frustrating. Although special glasses and lenses are not required to view the 3-D illusion, there are a few necessities. Depth perception and stereoscopic vision rely on the fact that you have two eyes with healthy vision. If you have vision in only one eye, or one of your eyes is extremely dominant over the other, the 3-D illusions of eye puzzles will be lost on you [source: Magic Eye].

Other issues with depth perception or eye conditions like lazy eye may also prevent you from seeing the image. If you wear glasses or contact lenses to correct your vision, this should not impede your ability to solve an eye puzzle. However, if you are nearsighted, you may want to remove your glasses to help you solve the eye puzzle more quickly. If you have healthy vision in both eyes and have not been diagnosed with any depth perception or other eye issues, you should be able to solve eye puzzles.


If you're having trouble, just be patient. Employ all of the different techniques until you find the one that works for you. If all else fails, there is a way to cheat and see the image in 2-D. Print or copy the eye puzzle onto two pieces of transparency paper. Lay one of top of the other and line them up perfectly. Then, move the top transparency slightly to the right. This should reveal the hidden object, but it won't jump out at you like the 3-D illusion was intended [source: Inglis].

If you do suffer from depth perception issues such as lazy eye or crossed eyes, eye puzzles might help improve your vision. Some eye doctors use 3-D imagery to help train the eyes and brain to work together properly. Although licensed optometrists have been successful in implementing this practice, usually referred to as vision therapy, there is no guarantee it will work for you.


Lots More Information

Related Articles

  • Bianco, Carl. "How Vision Works." April 1, 2000. (Aug. 28, 2011)
  • Calvert, J. B. "Stereopsis." University of Denver. April 24, 2005. (Aug. 28, 2011)
  • "Eye Exercises." Optometrists Network. 1995. (Aug. 28, 2011)
  • "History of Magic Eye 3D Pictures." Magic Eye 3D. (Aug. 28, 2011)
  • "How to See 3-D With Cross-Eyed Technique." (Aug. 28, 2011)
  • Inglis, Stuart. "Stereogram FAQ." June 6, 1994. (Aug. 28, 2011)
  • McEntegart, Jane. "How Does the 3DS Work Without 3D Glasses?" Tom's Guide US. March 24, 2010. (Aug. 28, 2011),news-6237.html
  • Pearce, Jeremy. "Bela Julesz, 75, Neuroscientist Who Studied How Brain Sees." New York Times Obituaries. Jan. 12, 2004. (Aug. 28, 2011)
  • Speck, Shane."How 3-D PC Glasses Work." Dec. 12, 2003. (Aug. 28, 2011)
  • "Stereoscope." North Carolina School of Science and Mathematics. (Aug. 28, 2011)
  • Thimbleby, HW and C Neesham. "How to Play Tricks with Dots." New Scientist. Oct. 9, 1993. (Aug. 28, 2011)