Your Ability to Judge Distance With Depth Perception

Judging Distances and Depth Perception Change with Arm Length

Your Ability to Judge Distance With Depth Perception

The justices of the Supreme Court may be among the best legal minds in the country, but they have no eye for distances — and new research may help explain why.

During oral arguments Wednesday (Jan. 15) in a case about the constitutionality of laws prohibiting protestors from gathering close to abortion clinic entrances, the justices were stumped at the size of the 35-foot-long (10.6 meters) buffer zone in question.

“It's pretty much this courtroom, kind of,” ABC News quoted Associate Justice Elena Kagan as saying. In fact, the courtroom is more than 90 feet (30 m) long. After a back-and-forth discussion, the deputy solicitor arguing the case clarified that the no-go zone is the size of the 3-point zone on an NBA basketball court.

But judging distances and depth may be trickier than it seems. A recent study, published Oct.

23 in the Journal of Neuroscience, finds that people's depth perception depends on their perception of their arm's length.

Trick someone into thinking their arm is shorter or longer, and you can influence how they perceive distances between two objects. [Optical Illusions: A Gallery of Visual Tricks]

Making judgments

Depth perception, the ability to judge the distances of objects from one another, is an important ability; without it, one would have no way of knowing that a marble in their hand and a basketball 6 feet away were actually two different sizes.

The human brain doesn't quite get depth right, however.

Research has shown that people overestimate the distance of an object closer than a few tens of centimeters away, and underestimate it for objects more than a few tens of centimeters away, where 1 cm is about 4 inches, according to study researcher Fulvio Domini, professor of cognitive linguistic and psychological sciences at Brown University, and his colleagues. This might help explain why a big distance ( 35 feet) is hard to gauge.

The area between these two boundaries is the sweet spot of depth perception, which makes sense: It's the region in which we're most ly to reach for something.

Because of this link between arm's length and depth perception, researchers had theorized that depth perception has to be flexible, in order to accommodate the changing length of the arm as people grow.

[The 7 Biggest Mysteries of the Human Body]

“When children start touching and playing with things, they don't just do it at any distance. They do it at a small range of distances,” Domini, who is also a senior scientist collaborator at the Istituto Italiano di Techologia (IIT) in Italy, said in a statement.

Perhaps, the researchers reasoned, the brain figures out exact distances in these important regions and then just extrapolates the rest.

Flexible perception

To test the theory, Domini and his colleagues first had 41 volunteers complete one of three perception tests — all in the dark, so they couldn't see their arms or hands.

In the first, the volunteers used a computer mouse to judge how far three rods in a triangular configuration were from one another. In the second, volunteers judged distances of these three rods by using their finger and thumb.

The third group was given a tactile test, in which they felt either one or two simultaneous gentle pinpricks on their forearms. The volunteers had to say whether they'd felt one poke or two.

After the tests, the researchers “trained” the volunteers to conduct virtual experiments: They placed motion-capture tags on the participants' forearms, and asked them to reach for a virtual cylinder on a computer screen.

Dots on the screen told them where their arm was in the virtual space. In some cases, the dots were accurate. In others, they showed the most outstretched finger as 6 in. (15 cm) farther out than it really was.

As a result, the volunteers felt their arms were longer than they really were.

Here's where things got weird: The volunteers tricked into thinking their arms were longer became better at judging the distance between both objects placed farther away from the viewer. In effect, the change in the perception of their arm's length had shifted their depth perception sweet spot.

The participants also got better at distinguishing one skin poke from two. This change in people's tactile abilities probably had to do with the perception of arm length, too, the researchers wrote.

The brain's internal image of the arm changed when volunteers were tricked into thinking the arm was longer, and that internal image change, in turn, seems to have caused a change in sensitivity.

“Even in adulthood, sensory systems are not fixed structures with immutable functions,” the researchers wrote in the paper describing the findings. The results show how flexible perception really is. They also may be important for researchers designing robotic prosthetics and human-controlled robots such as those used by surgeons.             

Follow Stephanie Pappas on and . Follow us @livescience, & . Original article on LiveScience.

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Depth perception

Your Ability to Judge Distance With Depth Perception

Seeing with two eyes helps people to judge distances and to see in 3D, but even using one eye, there are many clues (often referred to as visual cues) to give people depth perception. Depth perception using computers is more difficult.

Binocular vision – seeing 3D with two eyes

There are two main binocular cues that help us to judge distance:

  • Disparity – each eye see a slightly different image because they are about 6 cm apart (on average). Your brain puts the two images it receives together into a single three-dimensional image. Animals with greater eye separation, such as hammerhead sharks, can have a much greater depth perception (as long as the view from both eyes overlaps the same scene). This can be very useful when trying to catch fast-moving prey.
  • Convergence – when looking at a close-up object, your eyes angle inwards towards each other (you become slightly cross-eyed). The extra effort used by the muscles on the outside of each eye gives a clue to the brain about how far away the object is. If you hold your finger 20 cm in front of your eyes, your muscles need to work a lot harder than when your finger is 50 cm away.

These binocular cues are most effective for objects up to 6 m away. After this, the amount of eye separation does not give a great enough difference in images to be useful.

3D movies make use of disparity by providing each eye with a different image. However, the brain does not receive any cues from convergence as it normally would. This may cause discomfort for some people.

Monocular cues – 3D information from a single eye

If you close one eye, your vision becomes much less three-dimensional, but there are still many clues that allow you to judge distances. You are still able to pick up a pen, move around without crashing into things and even catch a ball.

Some of these monocular cues are as follows:

  • Accommodation – this is the change of focus when you look at a close-up object. The ciliary muscles inside the eye need to work harder to change the shape of the lens inside your eye. The effort required provides the brain with information about distance.
  • Sharp focus or blurry – if two objects are at the same distance, they will both appear to be in focus. Objects that are closer or further away will appear blurry.
  • Motion parallax – if you move your head, objects that are close to you will appear to move more than those objects that are further away.
  • Superposition – objects that appear to move in front of other objects must be closer (a little obvious perhaps, but very useful). You will often see some animals to move their heads from side to side or up and down. This gives important depth information both for motion parallax and for superposition. Try it out!
  • Vividness of colours – distant objects often appear less bright and colourful. This is due to the scattering of light as it travels from that distant object. Having more of the atmosphere to travel through means that light will be scattered more, so the colours will not seem as bright.
  • Definition and textures – close objects will have a lot of detail and definition apparent. More distant objects will not appear with as much detail. This is very noticeable when looking at a field of grass. Close up, the blades of grass will be noticeable. Further away, the grass is more of a sea of green.
  • Relative size – if we already have an idea of the size of two people or objects in a photo, this can give a good clue as to how far apart they are.

Artists use some of these monocular cues to give a perception of distances in a two-dimensional picture.

Creating 3D for movies, robots and security cameras

Computers and robots do not have brains to process these cues from digital images and interpret 3D information. For them, there needs to be an entirely different technology.

The article Light – polarisation provides insight on how 3D glasses work.

Activity idea

In the activity, Pinhole cameras and eyes students make a pinhole camera and see images formed on an internal screen. They then use a lens and see brighter and sharper images. This models the human eye.


Why Am I Losing Depth Perception After A Car Accident?

Your Ability to Judge Distance With Depth Perception

Are you confused or scared about what’s going on with your vision after a car accident? If you’re having trouble judging distances or seeing things that are far away, you might be suffering from depth perception loss. Read on to learn more about what this is and what you can do about it.

What is Depth Perception?

Simply put, depth perception is the ability to see objects in three dimensions and to judge how far away a given object is. Basically, when you look at an object, each of your eyes sends a slightly different picture of the object to your brain and your brain then puts these two images together so that you see the object. This happens at lightning speed so that you can see!

Depth perception generally requires the use of both eyes, so if you lose an eye or most of your ability to see one eye, you won’t have much depth perception. However, after a while, your brain gets used to only getting an image from one eye and is able to adjust its processing of images so that you can regain some of your depth perception.

If you lost your depth perception altogether, the world would appear completely flat to you. This is very uncommon but does happen occasionally, and this kind of severe problem can make it difficult not only to see but to navigate safely through your neighborhood or even your home.

Even without this kind of extreme loss of depth perception, you might be at extra risk of injury if you have depth perception problems. People with limited depth perception can’t judge distances very well, which is a problem if you’re driving. You might have a hard time judging when it’s safe to change lanes or whether you’re close enough to the curb when parking.

It also puts you at greater risk of accidental injuries, such as missing a step and falling on the stairs or falling off a curb while walking because you couldn’t distinguish it from the street. You might also have minor accidents such as spilling water while pouring it or become frustrated with tasks that used to be easy for you such as threading a needle.

Depth Perception Loss After a Car Accident

According to the American Optometric Association, it’s common for vision to decline slightly after age 60, but the loss of depth perception is not usually associated with age.

It most often occurs as the result of an injury to one or both eyes or because of muscle weakness in the eyes.

In addition, injuries to your brain can cause depth perception issues, since your brain needs to process the images from your eyes in order to see correctly.

A 2015 study showed that car accidents were the most common cause of eye injuries in children younger than 10, while adults most often injured their eyes in slips and falls.

However, hitting your head in a car accident can lead to a traumatic brain injury, which ly will result in a loss of depth perception.

Either way, it’s important to take depth perception problems seriously in order to prevent further accidents.

Ideas to Try If You’re Having Depth Perception Problems

If you’re having problems judging distances or depth of objects, your first stop may be your eye doctor. He or she can diagnose the issue and can recommend one of several accommodations to help you see better and move more easily and safely.

There are several options available for those with depth perception issues.

  • Occupational therapy. Occupational therapists help you regain skills after an injury to your brain and give you exercises to do to retrain yourself to see better despite a brain or eye injury.
  • Bioptic lenses. These are special lenses for people with poor depth perception that have a miniature telescope mounted on one or both lenses to help with perceiving distance and depth. These lenses can only be prescribed by an ophthalmologist and may or may not allow you to keep driving.
  • Reflective tape for stairs and curbs. One DIY solution to help protect you from slips and falls is to use reflective tape to help you see where all the steps in a staircase are or where the curb ends. The tape can help you be more aware of when you need to watch your step, especially at night when it is even harder to see.
  • Use of a white cane for navigation. You might have seen blind people walk with a white cane. That’s because a cane can be used to feel for objects in your path and alert you to their presence. This is as helpful for people with low depth perception as for those who are completely blind since lack of depth perception can cause difficulties with judging how far away objects are or seeing obstacles that you may trip over.

People sometimes feel embarrassed to use these tools. But remember: they’re there to help you avoid accidents! It might be worth it to try one or more of them and see how you feel afterward.


Depth perception problems can significantly interfere with your quality of life. Difficulty seeing objects at a distance can make it harder to complete everyday tasks pouring yourself a glass of water or threading a needle and can make it unsafe to drive or even to walk.

The good news is that there’s help available. In addition, if you lost depth perception as a result of a car accident, you might be entitled to compensation. Contact Smiley Injury Law today if you’d to schedule a consultation.

Learn More From Smiley Law Firm’s Injury Blog

Here at Smiley Law Firm we write about the topic of brain trauma extensively. We have a number of blogs and articles covering the following topics. Please read them and leave comments if you find the information helpful.


Depth Perception

Your Ability to Judge Distance With Depth Perception

Depth perception is the visual ability to perceive the world in three dimensions (3D) and the distance of an object.

Depth sensation is the corresponding term for animals, since although it is known that animals can sense the distance of an object (because of their ability to move accurately or to respond consistently, according to that distance), it is not known whether they “perceive” it in the same subjective way that humans do

Depth perception arises from a variety of depth cues.

These are typically classified into binocular cues that are the receipt of sensory information in three dimensions from both eyes and monocular cues that can be represented in just two dimensions and observed with just one eye.

[2][3] Binocular cues include stereopsis, eye convergence, disparity, and yielding depth from binocular vision through exploitation of parallax. Monocular cues include size: distant objects subtend smaller visual angles than near objects, grain, size, and motion parallax.

Monocular cues

Motion parallax

When an observer moves, the apparent relative motion of several stationary objects against a background gives hints about their relative distance. If information about the direction and velocity of movement is known, motion parallax can provide absolute depth information.[5] This effect can be seen clearly when driving in a car.

Nearby things pass quickly, while far off objects appear stationary. Some animals that lack binocular vision due to their eyes having little common field-of-view employ motion parallax more explicitly than humans for depth cueing (e.g.

, some types of birds, which bob their heads to achieve motion parallax, and squirrels, which move in lines orthogonal to an object of interest to do the same

Depth from motion

When an object moves toward the observer, the retinal projection of an object expands over a period of time, which leads to the perception of movement in a line toward the observer. Another name for this phenomenon is depth from optical expansion. The dynamic stimulus change enables the observer not only to see the object as moving, but to perceive the distance of the moving object.

Thus, in this context, the changing size serves as a distance cue. A related phenomenon is the visual system’s capacity to calculate time-to-contact (TTC) of an approaching object from the rate of optical expansion – a useful ability in contexts ranging from driving a car to playing a ball game. However, calculation of TTC is, strictly speaking, perception of velocity rather than depth.

Kinetic depth effect

If a stationary rigid figure (for example, a wire cube) is placed in front of a point source of light so that its shadow falls on a translucent screen, an observer on the other side of the screen will see a two-dimensional pattern of lines.

But if the cube rotates, the visual system will extract the necessary information for perception of the third dimension from the movements of the lines, and a cube is seen. This is an example of the kinetic depth effect.

The effect also occurs when the rotating object is solid (rather than an outline figure), provided that the projected shadow consists of lines which have definite corners or endpoints, and that these lines change in both length and orientation during the rotation.

PerspectiveThe property of parallel lines converging in the distance, at infinity, allows us to reconstruct the relative distance of two parts of an object, or of landscape features. An example would be standing on a straight road, looking down the road, and noticing the road narrows as it goes off in the distance.

Relative size

If two objects are known to be the same size (e.g., two trees) but their absolute size is unknown, relative size cues can provide information about the relative depth of the two objects. If one subtends a larger visual angle on the retina than the other, the object which subtends the larger visual angle appears closer.

Familiar size

Since the visual angle of an object projected onto the retina decreases with distance, this information can be combined with previous knowledge of the object's size to determine the absolute depth of the object.

For example, people are generally familiar with the size of an average automobile.

This prior knowledge can be combined with information about the angle it subtends on the retina to determine the absolute depth of an automobile in a scene.

Absolute size

Even if the actual size of the object is unknown and there is only one object visible, a smaller object seems further away than a large object that is presented at the same location

Aerial perspective

Due to light scattering by the atmosphere, objects that are a great distance away have lower luminance contrast and lower color saturation. Due to this, images seem hazy the farther they are away from a person's point of view.

In computer graphics, this is often called “distance fog”. The foreground has high contrast; the background has a low contrast. Objects differing only in their contrast with a background appear to be at different depths.

The color of distant objects are also shifted toward the blue end of the spectrum (e.g., distant mountains).

Some painters, notably Cézanne, employ “warm” pigments (red, yellow and orange) to bring features forward towards the viewer, and “cool” ones (blue, violet, and blue-green) to indicate the part of a form that curves away from the picture plane.


This is an oculomotor cue for depth perception. When we try to focus on faraway objects, the ciliary muscles stretch the eye lens, making it thinner, and hence changing the focal length.

The kinesthetic sensations of the contracting and relaxing ciliary muscles (intraocular muscles) is sent to the visual cortex where it is used for interpreting distance/depth.

Accommodation is only effective for distances less than 2 meters.


Occultation (also referred to as interposition) happens when near surfaces overlap far surfaces. If one object partially blocks the view of another object, humans perceive it as closer.

However, this information only allows the observer to create a “ranking” of relative nearness. The presence of monocular ambient occlusions consists of the object's texture and geometry.

These phenomena are able to reduce the depth perception latency both in natural and artificial stimuli.

Curvilinear perspective

At the outer extremes of the visual field, parallel lines become curved, as in a photo taken through a fisheye lens.

This effect, although it is usually eliminated from both art and photos by the cropping or framing of a picture, greatly enhances the viewer's sense of being positioned within a real, three-dimensional space.

(Classical perspective has no use for this so-called “distortion,” although in fact the “distortions” strictly obey optical laws and provide perfectly valid visual information, just as classical perspective does for the part of the field of vision that falls within its frame.)

Texture gradient

Fine details on nearby objects can be seen clearly, whereas such details are not visible on faraway objects. Texture gradients are grains of an item. For example, on a long gravel road, the gravel near the observer can be clearly seen of shape, size, and color. In the distance, the road's texture cannot be clearly differentiated.

Lighting and shading

The way that light falls on an object and reflects off its surfaces, and the shadows that are cast by objects provide an effective cue for the brain to determine the shape of objects and their position in space.

Defocus blur

Selective image blurring is very commonly used in photographic and video for establishing the impression of depth. This can act as a monocular cue even when all other cues are removed.

It may contribute to the depth perception in natural retinal images because the depth of focus of the human eye is limited. In addition, there are several depth estimation algorithms defocus and blurring.

Some jumping spiders are known to use image defocus to judge depth.

ElevationWhen an object is visible relative to the horizon, we tend to perceive objects which are closer to the horizon as being farther away from us and objects which are farther from the horizon as being closer to us. In addition, if an object moves from a position close the horizon to a position higher or lower than the horizon, it will appear to move closer to the viewer.

Binocular cues

Stereopsis, or retinal (binocular) disparity, or binocular parallax

Animals that have their eyes placed frontally can also use information derived from the different projection of objects onto each retina to judge depth. By using two images of the same scene obtained from slightly different angles, it is possible to triangulate the distance to an object with a high degree of accuracy.

Each eye views a slightly different angle of an object seen by the left and right eyes. This happens because of the horizontal separation parallax of the eyes. If an object is far away, the disparity of that image falling on both retinas will be small. If the object is close or near, the disparity will be large.

It is stereopsis that tricks people into thinking they perceive depth when viewing Magic Eyes, Autostereograms, 3-D movies, and stereoscopic photos.


This is a binocular oculomotor cue for distance/depth perception. Because of stereopsis, the two eyeballs focus on the same object. In doing so they converge. The convergence will stretch the extraocular muscles.

As happens with the monocular accommodation cue, kinesthetic sensations from these extraocular muscles also help in-depth/distance perception. The angle of convergence is smaller when the eye is fixating on far away objects.

Convergence is effective for distances less than 10 meters.

Shadow Stereopsis

Antonio Medina Puerta demonstrated that retinal images with no parallax disparity but with different shadows are fused stereoscopically, imparting depth perception to the imaged scene. He named the phenomenon “shadow stereopsis”. Shadows are therefore an important, stereoscopic cue for depth perception.

Disorders affecting depth perception

Ocular conditions such as amblyopia, optic nerve hypoplasia, and strabismus may reduce the perception of depth.

Since (by definition), binocular depth perception requires two functioning eyes, a person with only one functioning eye has no binocular depth perception.

Depth perception must be learned using an unconscious inference, which is much less ly to happen after a few years of age


Howard, Ian (2012). Perceiving in Depth. New York: Oxford University Press. ISBN 978-0-199-76414-3.Sternberg, R. K. (2012).Goldstein E.B. (2014, 2017) Sensation and perception (10th ed.). Pacific Grove CA: Wadsworth.

Over 360 Vivid Vision Providers prescribe virtual reality alongside patching and vision therapy to treat your lazy eye. Sign up through our doctor locator to see if Vivid Vision is right for you.


Depth Perception When Driving

Your Ability to Judge Distance With Depth Perception

It's night. You're driving. Something is coming toward you. But squint as you might, you can't quite tell just how far away it is.

If you struggle with depth perception while driving, especially at night, it can be pretty scary. But there's good news: There are ways to improve your vision to make it a safer, less stressful experience.

So check out our brief guide to improving depth perception behind the wheel. And find out why the problem might not be your eyes—it might be your car.

How does depth perception work?

Depth perception occurs when your brain combines pictures from both eyes into one 3D image. Depth perception is impacted when one eye is blurry or the eyes aren’t aligned, which can also cause suppression or double vision.

Use spatial clues

In addition to addressing any eye conditions, you can also develop your depth perception skills. That's because at longer distances the brain relies mostly on context clues to determine spatial relationships. Training yourself to identify these clues will enhance your depth perception and lead to a safer driving experience:

  • Motion parallax: Observe the relative speed of cars and other moving objects. Objects traveling at the same speed will appear faster when near and slower when far away.
  • Interposition: We can tell which object is closer or farther away how they overlap.
  • Aerial perspective: Color, contrast, and clarity (especially in regard to light) indicate how close or far something may be.  

Keep your car clean

Going to the car wash isn't just a matter of making your ride look sweet. When it comes to depth perception, it's also a matter of safety. Sure, most people realize that dirt on their windshield can hamper vision and lead to excess glare.

But even a small amount of grime on your own headlights can significantly reduce their output, leading to reduced visibility at night as well as eye strain. Simply keeping your windshield and headlights dirt-free could make all the difference in the world.

Use your tools

Every car comes equipped with tools designed to help drivers fight glare and see better at night.

But are you using these tools properly? Besides using your sun visor and dimming your rearview mirror, angling your side mirrors correctly can also diminish glare.

And those headlights you just cleaned? You may want to have a mechanic check them to make sure they are set at the proper angle as well. A few small adjustments to your car could make a huge difference for your eyes.

Beware of night vision glasses

A big craze these days (at least, if you believe infomercials) is the use of special amber or yellow-tinted night vision glasses.

But while these types of glasses can sometimes reduce glare, they accomplish this by diminishing the amount of light reaching your eye, meaning they can actually make it more difficult to see.

Luckily, there's a safer solution: Instead of using night vision glasses, consult your eye doctor about getting anti-glare Crizal® lenses. 

See your eye doctor

Speaking of which, if you have persistent problems with depth perception, particularly at night, you should check with your eye doctor to make sure it isn't a symptom of a larger issue.

For instance, decreased night vision is one of the early warning signs of a cataract. Or you may be battling a vitamin deficiency.

Seeing your eye doctor might do more than just help your driving—it may just save your sight.


What You Need to Know About Depth Perception

Your Ability to Judge Distance With Depth Perception
Home » Blog » Digital Health » What You Need to Know About Depth Perception

Sometimes understanding your eye problems is as simple as knowing what’s behind your symptoms. A term you might have heard, but not fully understood, depth perception, offers knowledge of one such problem.

Depth perception refers to the measure of your ability to see objects in three dimensions, and judge movement and distance. When you have depth perception issues, it generally links back to other eye problems.

Today we’ll help you administer an online depth perception test, and explain some of the implications of the results.

Depth Perception Test

Unless your eye doctor has already advised you on the subject, you ly can’t be sure if you have depth perception issues or not. So, to begin with, we’ll help you administer a quick test using the picture of a tennis ball below.

  1. Hold your extended index finger in front of the image of the tennis ball, roughly centered on the image, with your hand about six inches from your face.
  2. Focus your vision on the tennis ball. If your depth perception works well, you should see two slightly faint, slightly blurred images of your finger on both sides of the tennis ball. You should also be able to make out the complete image of the ball.
  3. Focus your vision, next, on your finger. Again, if the test goes well, you should see tow slightly faint, slightly blurred images of the tennis ball on both sides of your finger.

Follow the steps above, and you’ll have preliminary results. Whatever the results of the above test, of course, nothing matches the examination and advice of an eye doctor.

If you think you might have serious problems with your depth perception, meet with an eye doctor so they can help you evaluate the seriousness.

Either way, now that we have an initial understanding of your depth perception, we can discuss more of the details.

The Elements of Depth Perception

To have proper depth perception, you need stereopsis, also called binocular stereoscopic vision. Binocular here refers simply to the idea that both of your eyes work consecutively and together to make a unified image. If only one eye comprehends depth properly, it is called monocular. The elements of vision that affect depth perception, as well explained by, include:

  • Known size of an image on the retina: This is simply the eyes habitual memory of objective size.
  • Stereo Vision: This refers to how separate images in the eyes work together.
  • Moving Parallax: Objects at a further distance appear to move much slower than closer.
  • Retinal Disparity: Difference between what they eye expects and what it sees.
  • Fusion: The combined image of both eyes working together.
  • Interposition: Perception of overlapping objects.
  • Linear Perspective: The perceived size change as objects increase or decrease their distance from the eye.
  • Aerial Perspective: The color change eyes perceive at varying distances.
  • Light and Shade: Provides cues on shape and contour of an object.
  • Monocular Parallax: The change in relative perception of speed when you move your head.

The Causes of Depth Perception Issues

Often depth perception issues come in conjunction with other eye problems. Among those are the following:

Ways to Improve Depth Perception

If you struggle with depth perception issues, on their own or in conjunction with one of the above, combatting it should be a priority., once again, comes through with an excellent offering of ways to improve depth perception.

  1. Eye Rolling: Rolling your eyes around, deliberately and regularly, helps strengthen the eye muscles. In turn, your depth perception will improve with time.
  2. Shifting Your Gaze: Slowly shifting your gaze from one object to another, often in conjunction with eye rolling, sharpens acuity and perception.
  3. Resting Your Good Eye: If you have a stronger eye, try resting it specifically. This is the principle behind an eye patch when prescribed to someone whose eyes both work. Covering your strong eye allows it to rest, and strengthens your weak eye.
  4. Low Light: Your eyes have to work harder in highly lit areas. Allowing your eyes to rest in lower light if you are struggling with depth perception offers a much-needed break that will help your vision overall, and particularly your depth perception.

If you have depth perception issues, you ly also experience blurred vision (as mentioned above). Knowing the causes of blurred vision will help you get to the bottom of your eye troubles. Learn more today about blurred vision and how to respond to it.


Depth Perception, What Exactly is It?

Your Ability to Judge Distance With Depth Perception

Sure, we are all familiar with 3D, especially when it comes to movies and awesome special effects.

But have you ever wondered how your eyes are able to see three dimensions on a daily basis? It’s called depth perception – when the brain processes different pictures from each eye and combines them to form a single 3D image so that you can accurately perceive how far away people or objects are from you.

In order to have depth perception, you must have binocular vision, also known as stereopsis. If someone lacks stereopsis, they’re forced to rely on other visual cues to gauge depth. As a result, their depth perception is less accurate.

How to Test Your Depth Perception

There are simple ways to test yourself at home to determine if you have fully functional depth perception. To start, take a look at the below image of a baseball.

Now, hold up one finger, about six inches away from your face, in front of the image. Focus your eyes on the baseball and you’ll begin to see two somewhat transparent images of your finger on either side of the ball.

Next, focus your eyes on your finger. You’ll see two somewhat transparent images of the baseball on either side of your finger. This indicates good depth perception.

Next, test for eye dominance by holding your finger in front of the image of the baseball. Focus on the image and close your left eye. Your finger should appear to the left of the baseball.

Next, open your left eye and close your right eye. Your finger will seem to jump to the right of the baseball. This means that you have functional binocular vision (also known as stereo vision).

Below are signs that you may have faulty depth perception:

  • You can see your finger better on one side than the other.
  • The view of your finger is larger with one eye than with the other.
  • With one eye closed, the image of your finger appears right over the baseball, while with the other one the image of your finger is far to the left or right.
  • You can only see one image of your finger.

If you experiences any of these, we recommend that you schedule an eye exam with your eye doctor to see if your vision can be improved.

Common Causes of Depth Perception Problems

A range of conditions can affect your depth perception and cause problems. Some are harmless, while others are more serious, so it’s always good to check with your doctor if you’re experiencing issues.

  • Strabismus– a condition where your eyes don’t align properly and point in different directions. It can also cause double vision.
  • Blurred vision- blurry vision in one or both of your eyes can alter the image that’s sent to your brain and impair the convergence process. Blurred vision is a common symptom of several eye conditions, such as astigmatism, nearsightedness, farsightedness, and cataracts.
  • Amblyopia– commonly called  ‘lazy eye,’ this condition is when vision, even when fully corrected with glasses, is reduced in one or both of your eyes. Some common causes of amblyopia are strabismus (see above), refractive errors, and the inability of one eye to focus as well as the other.
  • Eye trauma – trauma to the eye, or having one eye, can reduce the quality of your depth perception. Many people with one functioning eye learn to judge depth perception using different signals called monocular cues.

How To Improve Depth Perception

One easy way to improve your depth perception is by wearing prescription glasses. However, if your depth perception is still off even with corrective lenses, you may want to try vision therapy treatments.

There are also exercises that you can practice at home to improve your depth perception. Before setting a plan on your own, we always recommend that you first consult with your optometrist. hey will be able to determine the best way to ensure that your depth perception is functioning to its best ability.


Understanding Your Depth Perception

Your Ability to Judge Distance With Depth Perception

The term depth perception refers to our ability to determine distances between objects and see the world in three dimensions. To do this accurately, one must have binocular stereoscopic vision, or  stereopsis.

If someone lacks stereopsis, they are forced to rely on other visual cues to gauge depth, and their depth perception will be less accurate.

Our eyes use three methods to determine distance:

  • The known size of an object on your retina: Knowing the size of an object from previous experience helps our brains calculate distance the size of the object on the retina.
  • Moving parallax: This is what happens when you stand face to face with someone and move your head side to side. The person in front of you moves quickly across your retina, while objects that are farther away do not move very much at all. This helps your brain calculate how far an object is from you.
  • Stereo vision: Since our eyes are about two inches apart, each eye receives a different image of an object, especially when the object is close up. When the object is far away this method does not work as well, since these dual images of objects appear more identical when the object is farther from our eyes.

What Are My Depth Cues?

We use a number of different tools for depth perception; these tools are known as depth cues. These cues are classified into binocular (both eyes), monocular (one eye), and inferred (combined binocular and monocular cues). A person’s ability to perceive distances and sizes depends on which cues are available to them.

The term stereopsis means that a person sees clearly with two good eyes, and sees images with stereoscopic vision. Someone who only sees with one eye lacks this tool and must rely on other cues to determine depth.

When someone uses both eyes to focus on the same object, their eyes converge. The convergence then stretches the extraocular muscles, and kinesthetic sensations from the extraocular muscles help with depth and distance perception. Other binocular cues include:

  • Retinal disparity: Retinal disparity simply means that each eye receives a slightly different image due to the different angle from which each eye views an object.
  • Fusion: When the brain uses the retinal images from the two eyes to form one object, it is called fusion. Fusion takes place when the objects appear the same.

Monocular cues allow a person to judge depth and the sizes of objects with one eye. Other monocular cues include:

  • Interposition: Interposition cues occur when there is an overlapping of objects
  • Linear perspective: When objects of known distance appear to grow smaller and smaller, the perception is that these objects are moving farther away.
  • Aerial perspective: The relative color and contrast of objects gives us clues to their distance. When scattering light blurs the outlines of an object, the object is perceived as distant.
  • Light and shade: Shadows and highlights can provide clues to an object’s depth and dimensions.
  • Monocular movement parallax: When our heads move from side to side, objects at different distances move at different speeds, or relative velocity. Closer objects move in the opposite direction of the head movement, and farther objects move with our heads.

What Are The Different Depth Perception Tests Out There?

There are two types of tests that are conducted to determine depth perception: the contour stereotests and the random-dot stereotest.

  • Random-dot stereograms are used to eliminate monocular cues. Examples include the Randot Stereotest, the Random-dot E Stereotest, and the Lang Stereotest.
  • Contour stereotests are used to evaluate two horizontally disparate stimuli. An example of a contour stereotest is the Titmus Fly Stereotest.

Which Problems Develop With Bad Depth Perception?

Problems with depth perception may develop when another condition is present. Common conditions that cause depth perception problems include:

  • Blurred vision: typically in one eye
  • Cranial nerve palsy: partial or full paralysis of the third, fourth, or sixth cranial nerves
  • Strabismus: misalignment of the eyes
  • Anophthalmos: absence of one or both eyes; may be congenital or due to trauma, infection, or other causes
  • Amblyopia

Consequently, problems with depth perception may cause additional problems such as:

  • Inability to perform normal tasks such as driving or reading
  • Children may have difficulty learning
  • Athletes may have difficulty performing in sports

How Can I Treat My Depth Perception Problem?

If you have a hard time perceiving depth, you have options. Vision therapy is the preferred way to treat depth perception issues. Vision therapists can train a person’s brain to fuse the images from each eye, or in the worst-case scenario, to ignore the image from the bad eye.

Eye doctors can also prescribe contact lenses or eyeglass lenses to hinder or block unclear images from the bad eye so they do not interfere with images from the good eye.

Depth perception exercises may also be useful. There are several different depth-perception exercises to choose from:

  • Eye Rolling: This exercise benefits those who may have weak eye muscles. Eye-rolling exercises help to strengthen nerve impulses that give us the ability to perceive depth properly. When beginning this exercise, slowly roll your eyes clockwise for a few minutes, then switch and roll them counterclockwise for a  few minutes.
  • Shifting the Gaze: This exercise is usually used in conjunction with eye rolling. While eye rolling, shift your gaze slowly, especially when first beginning the exercise.
  • Resting the Dominant Eye: When one eye is dominant over the other, the weaker eye will inevitably strain. This exercise involves covering the dominant eye for several minutes to allow the weaker eye to take over the vision responsibilities. This is usually done with an eye patch.
  • Low Light: Resting the eyes from light may improve poor depth perception. This does not mean go to bed earlier; it is more a regrouping for the eyes. Low-light situations ease pressure on the dominant eye without causing strain in the weaker eye.

Talking to Your Eye Doctor

If you or your child are struggling with depth perception, feel free to use these questions to begin a conversation with your eye doctor:

  • Which tests can we perform to determine whether I have a problem with depth perception?
  • Which eye exercises should I do at home? How often should I do them?
  • How else can we go about improving my depth perception?
  • Will a lack of depth perception interfere with my daily activities?
  • Will my depth perception gradually decline as I age?
  • What can I do to prevent my depth perception from diminishing?

Sources and References:
We have strict guidelines for each of our sources and references. We rely upon vision, eye and medical information from peer-reviewed studies, medical associations and academic research institions.

  • R.

    Atkins, MD “The Eye Care Revolution” (Kensington Books, 2004) 7

  • J. Di Girolamo “The Big Book of Family Eye Care” (Basic Health Publications, Inc., 2011) 96-97; 111
  • J. Weizer, MD; J.

    Stein, MD, MS “Reader’s Digest Guide to Eye Care” (Quantum Publishing, 2009) 72-73