How Depth Perception Works


Depth perception is the ability to perceive the world in three dimensions (3D) and estimate the distance to objects. Your brain accomplishes this by processing different images from each eye and combining them into a 3D image.

Depth perception allows your eyes to determine the distance between objects and determine if something is near or far from us.

Mamoru Muto / Aflo

For depth perception, you must have binocular vision, also known as stereopsis.

The most important aspect of binocular vision is having two eyes; People who rely on one-eye vision must rely on other visual cues to measure depth, and their depth perception is often less accurate .

Lack of accurate depth perception can make a big difference in your life, from early childhood education to the kind of work you can do.

The further apart your eyes are, the better your depth perception will be. Insects, animals and fish, with their eyes wide apart, have a particularly high level of depth perception.

Visual cues and depth perception

Monocular cues allow you to have a sense of depth even if you don't have two eyes working properly together, for example:

  • Parallax of Motion: This occurs when you move your head back and forth. Objects at different distances move at slightly different speeds, closer objects move in the opposite direction to head movement, and distant objects move with the head.
  • Interaction: when objects overlap, it gives us monocular signals about which one is closer.
  • Aerial perspective: Color and contrast cues tell us how far away an object can be. When light spreads, it scatters, causing fuzzy outlines that your brain interprets as more distant.

Reasons for poor depth perception

Lack of depth perception can be due to a variety of conditions. This includes:

  • Amblyopia : also called lazy eye. This is a condition in which one eye is weaker than the other. This usually occurs due to abnormal vision development during childhood and due to blurred vision in one or both eyes .
  • Optic Nerve Hypoplasia – Occurs when the optic nerve , which sends visual signals from the eyes to the brain, has not fully developed before birth. This can lead to partial or total loss of vision in children .
  • Strabismus : This occurs when the eyes look in different directions, for example, one looks straight ahead and the other looks inward or downward .
  • Blurred vision: Due to a variety of conditions, vision in one or both eyes can be blurry, much like an eye injury.
  • Injury to one eye: Trauma can change your vision temporarily or permanently .

Lack of depth perception can affect your life in several ways:

  • This can affect the child's ability to learn.
  • This can cause problems with driving and proper road navigation.
  • This can prevent the athlete from reaching their full potential.
  • This can prevent you from landing a job that requires a good sense of depth.

Depth perception test

A complete eye exam is the first step toward a complete evaluation of your depth perception.

An optometrist or ophthalmologist will first assess your vision by measuring your visual acuity or the quality of your vision. If one eye is very blurry and the other is not, your depth perception will be limited.

When an optometrist checks your eye muscles, they will do a follow-up test. The coverage test measures how well your eyes interact with each other and checks for strabismus.

Strabismus, like esotropia or exotropia, is a problem of the eye muscles when the eyes do not interact well with each other or when one eye is turned in, out, up or down. If the eyes are not perfectly aligned with each other, double vision or, more commonly, suppression occurs.

If your eyes are not aligned, your brain will suppress the image of the rotated eye so that you do not have double vision. As a result, you really only use one eye. When this happens, you will not have good depth perception.

Subtle levels of depth perception are measured by tests such as random point stereograms or stereo contour tests. Some of these tests are for young children and use cartoon characters to help the doctor determine if the child is using binocular vision.

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