How to Test Depth Perception

Medically reviewed by Johnstone M. Kim, MD

Depth perception is an integral part of everyday life. It is needed when determining distance and how quickly an object is moving toward you. Whether you are crossing the street or passing another car, depth perception keeps you at a safe distance.

If you have trouble perceiving distance, a depth perception test can determine how both of your eyes work together to see in three dimensions. This can be done at home or in an optometrist’s office.

Depth perception testing can help your eye care professional recommend exercises or corrective eyewear that help improve this aspect of your vision.

This article covers how depth perception works, instructions on how to test it, the causes of poor depth perception, and ways to improve it.

What Is Depth Perception?

Depth perception is the ability to see things in three dimensions, including length, height, width, and distance. Depth perception works through convergence, which generally happens when both eyes focus on the same object, stretching the extraocular muscles that control the eyeball’s movement within the socket.

When both eyes are focusing on the same object, each eye sees it from a slightly different angle. The brain compares and processes each eye’s information to form the unified image that you see.

When both eyes see clearly and the image is processed efficiently, that result is called stereopsis. When this doesn't happen as it should, the process of seeing depth becomes more complicated. At least 12% of the population has some problem with their binocular (two-eyed) vision.

People who see through one eye, or have monocular vision, may have some trouble with depth perception. Over time, the brain may adjust to using the limited visual information that it gets from one eye to form an image, and this usually results in acceptable depth perception.

The consequences of poor depth perception include:

• Inability to perform tasks, such as driving or reading

• Learning challenges in children

• Difficulties playing sports

How to Test Depth Perception

You can do a depth perception test on your own or have it done by an optometrist.

At-Home Test

Before making an appointment with an optometrist for a depth perception test, you can try a home test to check your depth perception.

Perform these steps to test your depth perception:

1. Draw and fill in a circle on a piece of paper. Post it on a wall.

2. Hold your index finger in front of the circle between your eyes and the paper.

3. Focus your eyes on the circle. You should see it clearly. Your finger, however, will appear slightly blurry and a bit transparent. It will also seem like there are two fingers instead of one.

4. Now, focus on your finger. The two images of your finger that you saw in the previous step should merge together, while the circle appears to be duplicated.

Repeat this process a few times to see if your results change or stay consistent.

Make an appointment to see your optometrist if you see any of the following during your home test:

• One finger is easier to see than the other

• One finger is larger than the other

• Fingers appear and disappear

• One finger drifts directly over the circle, while the other finger is far to the left or right

• You always see just one finger

These are indications that one eye is more dominant than the other, which can cause poor depth perception.

Getting Tested By an Optometrist

A comprehensive eye exam by an optometrist will usually include a depth perception test.

They may ask you to put on a pair of 3D glasses and look at a booklet of test patterns. Each pattern has four small circles, and you will be asked to determine which circle in each pattern looks closer to you than the other three circles.

If you can correctly identify the closer circle in each pattern, you are probably experiencing what is considered normal depth perception.

There are two types of depth perception tests:

• Random-dot stereograms: Also referred to as the Randot Stereotest, the Random-dot E Stereotest, and the Lang Stereotest, these are used to eliminate monocular cues or signals. These tests use two images, each composed of black and white dots or squares. While each eye sees a different pattern in the dots, when seen together, the patterns are viewed as a specific shape.

• Contour stereotests: The Titmus Fly Stereotest evaluates two horizontally different stimuli. The person taking the test looks at images (like that of a fly) and is instructed to identify the one that seems to be popping out of the page.

Causes of Depth Perception Problems

Some conditions that can cause depth perception problems include:

• Blurry vision: There are several potential causes of blurry vision, including anything from nearsightedness to glaucoma or diabetic retinopathy. Anything that makes vision blurry can interfere with depth perception.

• Strabismus: This condition is caused by a lack of coordination between the eyes that leads to the eyes crossing in or turning out. When the two eyes don't focus on the same image, depth perception is reduced or absent.

• Amblyopia: Also referred to as lazy eye, this occurs when the eye and the brain are not working together properly. The brain favors the other eye to compensate. The vision in the other eye gets weaker, which then causes poor depth perception.

• Nerve problems: The optic nerve is a bundle of more than a million nerve fibers that carry visual messages. If it gets swollen, inflamed, or damaged, vision loss and changes in depth perception can occur.

• Eye trauma: A direct blow or injury to one or both eyes could impair vision, which could affect depth perception.

How to Improve Depth Perception

The best ways to improve depth perception depend on the cause. Coping strategies can help when poor depth perception is a chronic issue.

Eye Exercises

Depth perception exercises that may help:

• Eye rolling helps strengthen nerve impulses that create awareness of proper depth. When beginning this exercise, slowly roll your eyes clockwise for a few minutes, then switch and roll them counterclockwise for a few minutes.

• Shifting your gaze: While rolling your eyes, shift your gaze slowly, especially when first beginning the exercise.

Treatments

Vision therapy can help in treating some depth perception issues. Vision therapists train a person’s brain to blend the images from each eye or ignore the image from the eye that is not as cooperative.

If amblyopia is the cause, treatment involves forcing the brain to use the eye with reduced vision by placing a patch over the strong eye or using medicine to blur the vision in the strong eye. This approach trains the brain to use the weaker eye.

With strabismus, an optometrist may prescribe eyeglasses to straighten the eye. Sometimes, surgery on the eye muscles is needed to straighten the eye.

Coping With Poor Depth Perception

When depth perception is a long-term issue, many people use a combination of strategies to help them in their daily life.

Here are some ways to adjust for changes in depth perception:

• Improve lighting in your home and office by adding desk and floor lamps or more ceiling lights

• Keep paths around the house clear of obstacles

• Touch objects, walls, etc. to get a better sense of location as you move through a space

• Get used to turning your head in both directions to see a more complete picture of your surroundings

• Put colored tape at the edge of stairs and steps

• Use handrails when available

• If driving is approved by your healthcare provider, reduce glare by dimming the rearview mirror, angling the side view mirrors, and limiting night driving

Anyone with depth perception issues should visit their eye doctor once a year for a vision check.

Read the original article on Verywell Health.