Michael Cole, OD, Child and Family Eye Care Center



Depth perception is one aspect of vision that is tested on nearly every patient in our clinic. You might find it surprising to hear that most patients who are found to be unable to see in 3D are not aware that they lack this skill. Most people in this situation use what we call monocular cues to guess distances. For instance, we know an object getting larger is likely getting closer. We use perspective to gain some information about depth. We also know that if an object obscures our view of another object, it must, therefore, be closer to us. So, what sets those skills apart from actual 3D vision?

Three-dimensional perception happens when our eyes each take a separate picture of the scene we are looking at. Due to each image being generated from different angles, our brain can combine the two slightly dissimilar images below into a single representation of space that is no longer flat.

Try this exercise that illustrates this phenomenon: Cross your eyes until you see two separate sets of the images on the right. Allow the photos to partially overlap so the central two boxes are superimposed on top of one another. You should see three boxes instead of two. If you focus on the center image, you will see this scene in three-dimensional space!

For this process to be possible, a few conditions must occur. First, both eyes must be “turned on,” or, in other words, neither eye’s input can be ignored by the brain. In addition, both eyes must be aligned at the same target and distance with one another. If an eye turn is present, a person will either see double, or one eye must be suppressed to avoid double vision. Lastly, both eyes must be relatively equally focused. If the refraction (glasses prescription) in one eye is greatly different than the other, the information from both eyes will not match and the brain will be unable to use both at the same time. In short, if both eyes cannot be used at the same time, we cannot see in 3D.

This happens in real life almost constantly, but we can also replicate this artificially with specialized optics and other uses of technology. For example, in a 3D movie theater we wear glasses that are polarized in different directions — one horizontally and one vertically. This allows the theater to project two images onto the same screen that are also polarized. With this setup, we see an image with one eye and the other image with the fellow eye. If you take the glasses off and view the screen without, you will notice two similar images superimposed on one another, but they are slightly offset. When these two images are combined, we are suddenly immersed in a movie experience that seems to jump right off the screen all around us.

In our clinic, we help people see in three dimensions for the first time in their lives quite regularly. Our vision therapy program enables us to  re-train the visual system to make this process happen the way nature intended.

Technology has greatly enhanced our ability to train the visual system. For example, in our clinic we have equipment that utilizes 3D television optics to show each eye a different image. With this tool, we can manipulate and move these images to enhance coordination of the two eyes. Another instrument in our office utilizes virtual reality technology allowing an immersive experience in which we can control the amount and type of information flow to each eye. In clinics across the country, this instrument has changed the way “lazy eye” is treated and has enhanced our outcomes more than were previously thought possible.

Depth perception is the peak of performance regarding the visual system, and an outcome that we desire for all who are treated in our clinic. If you have any questions, or would like to schedule an appointment, please contact our office.