The first time I put on a pair of yoked prisms during a vision therapy appointment, I almost fell over. I immediately felt lost in a swirling room that had, 30 seconds earlier, felt very different. The walls were moving and when I reached to touch the objects around me, they weren’t in the correct spots. Walking down a straight line was laughable and every time Dr. Dan tossed a bean bag to me, it either hit me, or the floor.
After weeks of using the yoked prisms with exercises everyday, my brain learned to adjust. By opening my periphery and being aware of the whole room I was able to easily complete the work with yoked prisms that had seemed impossible at first.
But why does any of that matter? It’s not like I need to learn how to navigate life in a distorted world. Or do I?
What are Yoked Prisms?
Yoked prisms are glasses many times used in vision therapy. There are a variety of strengths, but generally, they are between 5 and 15 prism diopters. The higher the strength, the more slanted the lens is and the more the world shifts when you put them on.
This article is about high strength yoked prisms that are used during vision therapy activities. Sometimes a lower strength prism is put in prescription glasses to help the brain process information more easily. It’s so amazing and can have awesome results, but that is not what I’m talking about here.
When looking through a high strength prism, the image that is being focused on shifts according to the strength of the prism. The light is bent as it goes through the lens.
Picture 1: Imagine looking at a water bottle directly in front of you. You could easily reach out and grab it. Where the water bottle is in space matches what your eyes and brain are telling you it is sitting.
Picture 2: Now put on a pair of yoked prisms and everything in your visual field will shift. In the picture it shifts right, but most yoked prisms allow you to turn the prism so that it can face left, right, up or down.
As you look at the star, the glasses actually make it appear in a different place in space than directly in front of you. So even though you may perceive that the star, or water bottle is over to the right, when you reach there, you will realize that it is several inches further to the left. Over time, your brain learns to adjust.
Things also appear shorter, taller, wider and skinnier depending on which way the prism is faced and what your are looking at.
Wearing a yoked prism is like being in one of those crazy mirror rooms at a carnival. Nothing looks or feels “normal.”
How Can Yoked Prisms Help with Strabismus?
When a person is born with strabismus, their brain automatically learns to adjust to a distorted world where each eye is pointing in a different direction.
After 33 years with strabismus, my brain had mastered vision with strabismus, but trying to unlearn that version and relearn the version where I use both eyes presents a very challenging task!
I have to unlearn everything my brain has worked so hard to develop and then reteach my brain a more efficient and effective way to use the visual system. Unfortunately, as human’s age, their brain’s are less and less excited about changing or relearning a new way of seeing.
Yoked prisms can play a major role in helping with the process though.
Optometrist Robert S. Fox taught that yoked prisms “are a valuable tool in breaking down patterns that have developed over time that enable the patient to cope with their visual condition… The prism provides an ideal neurological stimulant to change the visual processing pathways of the brain.”
By using prisms, the brain learns to adjust and adapt to changing stimuli. Because prisms can be used while you are up and about, visual, vestibular and proprioceptive systems are all engaged and create an ideal situation for the brain to learn.
Dr. Fox continued, “This adds a tremendous amount of information in addition to the visual stimuli. It results in a greater number of problems to solve and the need for the patient to develop flexibility and be cognitively involved.”
“Since we live in an open, three-dimensional space world, this mode of therapy has tremendous carry-over to the real world.”
Where can I Purchase Yoked Prisms?
If you have to ask this question, you probably aren’t an Optometrist or Vision Therapist. Because they are considered medical equipment, yoked prisms can only be purchased through a licensed optometrist. So unless you are licensed, you can’t buy these. My Optometrist sent a pair home with me for several weeks to use in at-home activities so I haven’t decided to try to purchase my own through him, at this point.
What Exercises Can I do with Yoked Prisms?
If your optometrist sent you home with yoked prisms and you’re wondering what to do with them, here are some different activities to try at home. The key is to remember WHY you are using them. We want our brains to learn to adjust and transform and exercise their plasticity. Engage the vestibular system and get proprioception and touch involved. I found that using my sense of touch has been HUGE in my success.
Your Optometrist will probably use the yoked prisms in their office with a variety of therapy activities like the Brock string or Gem, I’m not going to go into what is done during therapy appointments, since I’m not an optometrist, I’m just going to go in to some fun ways to do your at home activities with your yoked prisms.
Okay, put on your glasses, let’s dive in!
Your Optometrist will probably send you home with some basic activities and you can use your imagination to come up with your own, but here are the activities that I used!
Bean Bag Activities
- Bean Bag Partner Toss- Toss and catch a bean bag with another person using your left and right hand. You can alternate between hands or do 10 with the left and then 10 with the right, etc.
- Double Bean Bag Partner Pass- Each partner holds a bean bag and on the count of three, both throw it to the other person and try to catch. Change the difficulty by switching hands or using a metronome!
- Walking Toss- Toss a bean bag with a friend while you walk forward and backward.
- Bean Bag Rainbow Toss and catch a bean bag in the air to yourself from your left to right or right to left over your head like a rainbow. Make sure to use peripheral vision to keep the bean bag in view.
- Single Hand Bean Bag Toss – Using either your right or left hand, toss the bean bag into the air and catch it with the same hand.
- Juggling- Start with two bean bags and try adding in a third to challenge yourself.
- Bean Bag Bowling– Set up an object on the floor (cup, water bottle, toy, etc) and try to hit it. This works great if you have multiple beanbags. Try to hit the object, but you will probably be off at first. Notice that after throwing 5 or 6, your brain adjusts and starts becoming more accurate.
- Bean Bag Basketball- Find a basket, bucket, bowl, or cup and try to toss the bean bag into the object. The smaller the container, the more difficult. You can also back up or scoot closer to adjust difficulty. Again, it’s nice to have multiple bean bags so that you can see your progress
Pointing/Touching Activities – Start by pointing with your fingers, increase the difficult by pointing with a stick; rhythm stick, drum stick, chopstick, sword, etc.
- Door Corners- Stand in front of a door, alternate hands and point to each corner on the design. Focus on touching it exactly in the corner first try. It will be hard and you will miss at first. But as you relax your gaze and try to see the whole room it will get easier and your brain will learn, it is amazing to watch!
- Dodge the Blinds- Find a window with blinds and stand in front of it. On each level, alternate hands and try to poke your finger between the slats, as close to the strings as possible without touching them. You can move up and down or left to right to mix things up. It seems simple, but is great for giving feedback to your brain about where in space you and the blinds are.
- Squat Squishers- Use stickers, post it notes, or pieces of painter’s tape to make several spots on the wall (if it’s for a child, these bug stickers are perfect) . Do half at eye level and then the other half way below so that you’d need to squat to get them. Alternate hands and high/low to touch or “squish” each bug. Start slow and add speed as long as the accuracy stays solid.
- Color Call- If you have kids, they will LOVE this one! Get several cups (or anything, really) and set them on a counter or table upside down. Have a child call out colors, when they say a color, you hit that cup. Start by using your whole hand, then one finger, than a stick. Make sure to alternate hands and have fun.
- Play the Piano (or other instrument)- If you have a piano, try playing it. I used music much easier than I usually play and tried to keep my eyes on the music and use peripheral to see my hands. The piano is amazing because you get instant auditory feedback if you misplay a note.
Full Body Activities-
- Walk the Line- Put a piece of tape across the floor and walk heel to toe across it, making sure to stay on it while keeping your focus on something straight ahead. Go forwards and backwards.
- Knee Raisers- Using the same line, walk heel to toe across it, but before you take the step, raise your knee and touch it and then step onto the line. Go forwards and backwards. Keep your focus on something straight ahead.
- Side Lifts-Using the same line, walk heel to toe across it, but before you take the step, raise your leg to the side then step onto the line. Go forwards and backwards. Keep your focus on something straight ahead.
- Soldier Walk- Using the same line, walk heel to toe across it, but before you take the step, lock your knee and swing your leg straight forward and swing the opposite arm straight forward then step onto the line. Go forwards and backwards. Keep your focus on something straight ahead.
- Bend Over Walk- Using the same line, walk heel to toe across it, but before you take the step, bend over so that your back is flat, then take the step and return to the upright position and put your focus back in front of you. Go forwards and backwards.
- Stairs- Only do this if you have a safe place to do it. Somewhere with just a few stairs would be ideal. Go up and down while keeping your focus forward. This is especially great when the prism is pointing up or down.
- Don’t Step on a Crack- If you have tile in your house, start on one side of the room and walk across the room without touching a crack.
Yoke Prisms Combined with Therapy – Yoked prisms can be used in combination with many vision therapy activities. They can help the brain have enhanced communication between all of the different systems; visual, vestibular, auditory, proprioceptive, etc which means that maybe you’ll start having more success with your therapy activities.
I’ve done everything from pencil pushups and tracking exercises, to the Gem Vectograph and Brock String while wearing yoked prisms during my vision therapy appointments.
Ask your therapist and they may assign you to add yoked prisms to one of your normal exercises, or add them as their own exercise to up level your brain and it’s amazing work!
Teach your brain to use all of it’s systems together and your success will be multiplied. Just two weeks after I started using the yoked prism on a daily basis at home, I experienced stereopsis in real life for the first time. Read about it here. It was awe inspiring and so beautiful. Yoked Prisms weren’t the only thing I was using, but they definitely have played a part in my success.
No one exercise is going to make all the difference, it’s consistent daily efforts with a variety of treatments that allow your brain to reprogram and relearn a new, more amazing way to see the world with both eyes!