Followers have asked me to create more multilingual videos. I was too busy over the past five years making the film Saved by Language, promoting the film and writing the book, One-Eyed Princessto dedicate time to record videos in various languages. I have recently released a series of videos in English, SpanishRussianFrenchPortuguese, and Italian about binocular vision problems (what it’s like to see when the two eyes don’t work together).

Lack of correct medical information in various languages => Global public health problems

Between 2-5% of the population has asymmetric eyes (eyes that aren’t straight) and has binocular vision problems, yet most of the information about binocular vision problems is in English. I decided to communicate what I know and make it accessible to people whose languages I speak.

Doctors don’t know the truth => Patients suffer

Medical doctors often know little or nothing about the impact on the lives of patients whose eyes do not work together and who may not see in 3D (have depth perception).

Patients and their parents don’t learn that the patient’s lack of depth perception and binocular vision may account for problems with:

  • reading
  • pouring liquids into containers
  • difficulty walking down stairs
  • bumping into things (knowing where one is in space)
  • playing sports involving hitting, kicking, catching balls
  • driving
  • parking
  • having balance
  • other activities involving the eyes working together

Ignorance about one’s own vision ≠ Bliss 

I didn’t know until I was in my 20s that I was partially blind. No doctor told me.

Some patients are misdiagnosed with attention deficit problems and take dangerous drugs, when what they really need are corrective lenses and vision therapy.

Watch and share!

You likely know someone who has binocular vision problems and may not know the impact their impaired vision has on their daily lives.

Topics covered:

  • amblyopia
  • strabismus
  • convergence insufficiency
  • how not seeing in 3D impacts the daily lives of people who lack stereovision
  • vision therapy
  • misdiagnosis of ADD & ADHD
  • strabismus surgery
  • prisms
  • medical malpractice against doctors who don’t inform their patients about their binocular vision problems and more.
  • false information promoted by a Harvard Medical School professor without proof in peer-reviewed scientific journals

Links to other videos: SpanishRussianFrenchPortuguese, and Italian

This is the video in English. See below for the transcript.

Click “CC” for captions in English.


Binocular vision problems

Susanna Zaraysky, author of One-Eyed Princess


I’m speaking today about the lack of awareness about binocular vision issues.

When people see with both eyes, they have binocular vision. If somebody only uses one eye, they have monocular vision.

It’s very poorly known that there’s a significant portion of the population that doesn’t see with both eyes or who has trouble using both eyes together.

Estimates show that about two to five percent of people, like me, have asymmetric eyes. We have either amblyopia, commonly referred to as a “lazy eye” or strabismus, known as “crossed eyes” or both conditions. Even when both eyes are symmetric, but one is much weaker than the other, a person can have amblyopia.

Even if both of our eyes are functioning, the brain can’t process the image from both eyes to fuse and to create a 3D picture. One eye sees an object in one place and the other eye sees it nearby. To prevent double vision, the brain shuts off the vision from one eye and processes the vision from the other eye, or the brain switches very quickly from eye to eye. As a result of only seeing with one eye, we don’t see in 3D. We don’t have depth perception. These types of stereovision problems also occur in those who are blind in one eye, have some form of cataracts, nystagmus, a traumatic brain injury or have other conditions.

I was born cross-eyed. As you can see in this picture, I was born with both eyes looking in different directions. At the age of three, I had my first operation to straighten my eyes and that operation left me with a lazy eye. When I looked at people, they didn’t know which eye to look at because one eye would look at them and the other eye was wandering off. I had my second operation at the age of 17 to straighten my eyes. Since that operation, my eyes appear to be straight. But I am still cross-eyed because both my eyes are not symmetrical.

When I was a child, I used to think I had magical vision.

Before I put on my Coke-bottle-thick glasses in the morning, I looked at objects by my bed and the objects would move. I thought I was moving them with my magic power. What I didn’t know at the time, was that my brain was switching from eye to eye and each eye saw the object in different places. It appeared that the object was moving, but it was just my brain switching from eye to eye.

After my second operation, I thought I could see like everybody else because my eyes looked straight and I no longer saw objects moving. I had done vision tests in school and at the Department of Motor Vehicles to get my driver’s license. I passed them because I only had to read a simple eye chart. There was no test for binocular vision.

I went to ophthalmologists, and to a neuro-ophthalmologist, all of whom were specialized in binocular vision issues. All of these doctors knew that I had strabismus. None of them asked me if I had any trouble driving, reading, in sports requiring me to hit, kick, throw or catch a ball, walking down stairs, if I found that I was very clumsy, if I had trouble pouring liquids and if I had bad hand-eye coordination. Nor was I ever tested with polarized lenses or red-green glasses and informed of the impact of my lack of depth perception.

My ignorance was not bliss.

I didn’t understand why my heart would beat really fast every time every time I had to merge on the highway or why it was so hard for me to parallel park and why I tried to avoid driving at night. I never understood why I held onto the handrail while walking downstairs, like an old lady. I needed to feel where I was in space. Otherwise, it was hard for me to see the distance from one step to another.

I read an article by Dr. Oliver Sacks in the magazine, The New Yorker, about Sue Barry, who also, like me, had been born cross-eyed and developed 3D vision by doing binocular vision therapy. I was shocked. I took the article to my optometrist and asked, “Doctor, am I like this woman? Do I not see in 3D?” The doctor performed a couple tests, with polarized and 3D glasses and 3D images. I couldn’t see the distance between one image or the other.. He said, “You don’t have depth perception.”

I was furious that no doctor had ever told me that I was partially blind and how this blindness impacted my life.” Finally, I understood why it was so hard for me to drive, why I was so clumsy at different partner dancing and sports.

I didn’t see where balls were in space. If I was trying to hit a tennis ball, I would hit all around me because I couldn’t figure out how far the ball was away from my racket.

I decided to do vision therapy with tools like prism glasses and the Brock string after reading Susan Barry’s book, Fixing My Gaze, about how she developed binocular vision via vision therapy. Very quickly, my vision changed.

I could clearly see the rain outside a window. Before, I only knew it was raining if I could hear the rain or if I saw object outside, like a fence, that was wet.

I looked at orange peels in absolute awe because I could see the indentations of the orange skin.

I walked in parks and it looked like the leaves of trees were coming towards me. I was seeing depth in motion.

I was awed at this new world. When I described it to my friends and family, many of them looked at me as though I were from another planet.

I went to various medical professionals to get help with the double vision, headaches and fatigue that were side effects from the therapy. Most of the professionals had never heard of vision therapy, had never met anyone who couldn’t see in 3D and couldn’t help me. I felt alienated from most of the people in my life because they didn’t understand what was going on with me.

I’ve spoken to both brain and eye doctors and I’ve learned that they unfortunately don’t learn about what it’s like to only see in 2D.

Prof Margaret Livingstone, a neurobiologist at Harvard Medical School, spoke on the BBC and said that not seeing in depth with both eyes didn’t present any major deficits according to her friend, who was born without stereo depth perception, it was only a problem when trying to thread a needle. That claim is terribly wrong.

What is important to note is that there is a spectrum of binocular vision impairments. Some people with a slight eye turn have more depth perception than I do, while others with more severe eye turns have less depth perception than I do. You can’t say that because one person’s limited depth perception is not a problem for them that in general binocular vision disorders are not a hindrance.

If you’re a parent of a child with a binocular vision problem, try out this eye patching challenge to understand how your child experiences the world.

If you’re one of those doctors who is honest enough to admit that you have no idea what it’s like for your patients who can’t see in 3D, take on this eye patching challenge.

Patch one eye. Don’t do it during the work day to avoid embarrassment, questions and accidents. At home, patch one of your eyes to see in 2D. For some of you, you’ll close one eye and you’ll still see in 3D. That’s because your brain is making up for what you just closed with one eye. Eventually, your brain is going to stop supplementing your impaired vision and only show you a 2D picture. Walk around your house. Walk downstairs. You’ll probably start bumping into things. Try to pour water from a jug.

Don’t drive with one eye patched! Patch one eye and sit as a passenger in a car when somebody else is driving and look in the rearview mirror, look at the side windows and see how well you can determine how close cars are while the driver is merging, changing lanes or parking.

Don’t cheat and stop after 15 minutes or after your first time bumping into something. Take on the challenge for real for two weeks. You need to simulate limited depth perception in various environments to truly empathize with your patients or children.

Doctors, consider the legal and ethical consequences of not disclosing the truth.

It goes against medical ethics for doctors not to tell their patients and the families of the patients that patients are partially blind. Not seeing in 3D is a partial blindness. Imagine what it’s like for your patients to drive and crash their parents’ car because they literally couldn’t see the other cars that were merging. Patients have a right to know what’s going on with their bodies, brains and perception.

If you’re a medical professional and have not informed your patients with binocular vision problems of the impact of their hidden disability, you could be liable for a medical negligence lawsuit. If you’re an ophthalmologist who did not tell binocular vision patients who opted for surgery to cosmetically straighten their eyes that there are non-surgical alternatives to surgery, prism glasses and vision therapy, you are liable for medical malpractice lawsuits.

Doctors, you can’t just ask a patient, “So, tell me about your depth perception.” If your patients have a hidden disability, and lack something, they don’t know you’re missing it unless someone tells them or they read about it. It’s like asking a color blind person if they miss not seeing red. If the person never knew red existed, they don’t know they’re not seeing it. The Father of Modern Medicine, Dr William Osler said, “Listen to your patient, he is telling you the diagnosis.” You have to inquire with your patients about how their vision impacts their life and ask them questions about reading, walking downstairs, hand-eye coordination, sports and other activities requiring binocular vision.

There is another binocular vision condition called convergence insufficiency. The patient has trouble converging their eyes to read. Since most schools don’t test for binocular vision problems, convergence insufficiency goes undiagnosed. The problem is that people with this condition need help from a vision therapist and developmental optometrist trained in helping people with binocular vision problems so that they can read.

Can you imagine what it would be like for your child, who sees things moving on the page and they don’t understand why and they don’t understand that there is something wrong? Sometimes these kids misbehave in class because they can’t read and are frustrated. They are misdiagnosed as having Attention Deficit Disorder (ADD) or Attention Deficit Hyperactivity Disorder (ADHD) and given dangerous psychotropic medications such as Adderral and Ritalin that have terrible side effects such as insomnia and suicidal thoughts.

Pediatricians or psychiatrists who have prescribed a medication to patients who really had convergence insufficiency or other binocular vision issues, you could also be subject to a medical negligence or malpractice lawsuit.

I’m making this video in various languages because I want to get this message to as wide of an audience as possible.

I’m not against strabismus surgery to straighten the eyes. I’m very happy that I had the surgery twice and stopped getting weird looks from people who didn’t know which eye to look at when speaking to me. However, had I known that I could have done vision therapy and used prisms to straighten my eyes and possibly create some depth perception without going under the knife, without the risks of surgery, I might have thought twice about getting the surgery.

I compiled my story in my book, One-Eyed Princess to raise awareness about binocular vision problems and therapy.

I’m not here to promote surgery, prism glasses or vision therapy. I’m here to promote education.

I’m not an anomaly. There are millions of people who have the same issue that I do. There are more of us who have binocular vision problems than there are doctors who treat binocular vision problems.

To find a developmental or behavioral optometrist specialized in binocular vision and to read more about these issues, please see the list of resources in the video description.

I invite you to speak up because you’re not alone. Thank you.


  1. Thank you for this. My daughter has just had surgery for strabismus. She’s 10 and has worn glasses and an eye patch for her lazy eye since she was 18 months old. It’s only in the last 12 months that I have become aware that she doesn’t have binocular vision and even more recently that I am beginning to realise the impact this has had on her life. All the years of watching her have difficulty negotiating stairs, catching a ball, bumping on to things. It all makes sense now.
    Not once was vision therapy mentioned by any of my daughter’s eye doctors. I only discovered it when I came across Sue Barry’s Ted talk.
    I am hoping to start her with vision therapy soon.
    Can you tell me how many sessions you had to do before you noticed a difference and do you have to continue to go or can you do the exercises at home?

    • I noticed a change after the first couple weeks, namely I saw more details, but I also became extremely tired. Soon after starting vision therapy, I developed intermittent double vision.

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