Answer transcribed from Brightway's Interview with Dr. Bryce Appelbaum: 

Great question! A question that I get asked essentially on a daily basis is after a stroke, let's say the number one most common symptom is double vision. What most practitioners or front-line healthcare workers do is give somebody an eye patch and say “well look you don't have double vision”. Now, this does get rid of double vision. However, it’s not allowing the brain the opportunity to get the eyes to work together and it's essentially forcing the brain to give up and to just attend to one eye's information.

A brain injury needs to be addressed on a brain basis, not on an eye basis. Oftentimes, surgery is recommended where the eyes are not acting like they're working together so we're addressing the hardware instead of the software. If you can think about double vision being a faulty mismatch in terms of somebody's perception of where something's located and where they're actually aiming their eyes, it needs to be addressed on an eye coordination basis. Keep in mind that rarely, double vision is related to inappropriate eye muscle strength or length. It's usually that coordination piece.

For double vision, there often are quicker fixes than vision therapy. They don't work for everybody but for some people, they can be very important and very helpful in making life more comfortable and decreasing symptoms. One of those options would be what can be done to a pair of glasses to help decrease or eliminate some of that double vision. With glasses, there can be the right combination of lens power that can help facilitate that or the right combination of prisms. Prism is essentially a fancy lens that changes where something is located in space. It distorts space so if somebody has an eye turn, that's 10 units and there's 10 units whether they're looking in or out, up or down, or left or right. 

You can get the right power prism so in that case, a 10 unit prism moves the visual world to where their eye is so that all of a sudden, their brain can take in both eyes and make sense of that. Most eye turns or double vision vary based on where the patient's looking, how fatigued they are, or how much new work they're doing. In which case, there's not really a prism number that would eliminate all of that. However, I'm a big believer of the weakest prism power or weakest lens power possible that gives the most improvement is really what we should be prescribing. 

You relate that to let's say high blood pressure. Somebody wants their blood pressure to be at 120 over 80 and let's say a 100-milligram pill gets you there and another 10-milligram pill gets you there. My model of practice is always do the 10-milligram pill because it's you're becoming less dependent on outside means. In some cases, just giving a little bit of prism can help allow for longer fusion or more flexibility with the internal and external muscular systems that control the eyes. 

That can be helpful in certain cases where somebody has some sort of acquired brain injury that may say their visual field to their right is no longer accessible. You can use what's called a yoked prism, which is not spelled like egg yolk. It moves the world to where they're less sensitive, so you can actually take the world and either move it to the right or take the world that's already on the right and move it to the left. It's easier for them to process and it's very common to have a visual midline shift with a head injury. Oftentimes, the body's egocentric center is as if it's not in the body center, so it's the left or the right or a different position. You can find that with the right measurements, you can find what their visual midline is and then how far it's decentered. Then with a yoked prism, move it to where the body center is so it can eliminate a lot of balance or coordination problems. 

On top of that, vision therapy is probably the best option for double vision in terms of raising the individual's awareness of what their eyes are doing. They can then figure out why they are seeing double and then get that feedback to know when it does happen. They have the tools in place to then compensate and eliminate the double vision. There are also lots of different types of prism or filters that can help block off the eyes working together at one particular position of space and aren’t a complete eye patch where they're not using it at all. You could have depth perception and alignment and down-gaze but maybe not up-gaze. That's where we can alter up-gaze to make it easier for the eyes to work together. A combination of the prism lenses as well as vision therapy is traditionally the approach here.

I would say almost everybody who's in vision therapy will have some sort of optical setup to help speed up the process and allow what's occurring outside of the therapy rooms to not act almost like anti-therapy. If you're taking steps forward in treatment but then staring at a computer screen all day and then embedding a bad habit, we want to make sure that we have a support system set up so that it interferes as little as possible. I kind of relate it to going to the gym to get in great shape. You're doing strength work, mobility work, and flexibility work but then you're going home and eating donuts all day. If you do this, you're still going to be in better shape than when you're not going to the gym but you're countering all the work that you're putting in. 

I think one of the biggest things we can do and one of the most often recommended habits to start engaging in is having a 20-20-20 rule. This means no more than 20 minutes of staring at a screen or reading without taking a break for at least 20 seconds and looking 20 feet away. By doing this, you’re relaxing the eyes and giving the brain an opportunity to rest and then come back to re-engage. A lot of people will say “oh that decreases my productivity and then I’m taking breaks and I don't like that”. However, if you're spending eight hours on the screen and you're taking breaks at least every 20 minutes, hopefully, more often, you're allowing yourself to operate at your potential for longer and there's going to be a drain on the system that's going to be introduced much later on in the day. 

I think the rule is always helpful but also having good lighting, posture, and the right lenses in place for supplementing auditory input with whatever is being presented visually are important as well. There's a multi-sensory integration approach to filtering and processing that input from different sensory sources. Therefore, we should engage in enlarging the print and making it so that it's easier for the eyes to focus on the target. Additionally, engage in three-dimensional space rather than an artificial plane, though it is really hard these days to do.

If you think of the focusing system, it's a sphincter muscle or a circular muscle, and it's behind people. So when you're looking at a screen, it's engaged and it's only relaxed or kind of disengaged when you look far away. I think a good example is if you were to squeeze your fist as hard as you can, after 10 seconds or so, your hand starts to hurt. However, if you can squeeze and let go and squeeze and let go, you can do that for so much longer than just holding it tight. Although this is a little bit of an exaggeration, if you stare at any particular distance where your eyes are not in their natural resting position, you're engaging the focusing system. 

Very often, what I see with patients with head injuries is they're actually using their focusing system at every distance, even in the far distance when their eyes should be relaxed and rested. That's the brain sending these impulses to the eyes to look at this particular place, but the system is so dysregulated that you don't know where to look. I think that's something where the more we can exercise our eyes and the more we can develop voluntary control over some of these systems, the more likely it's going to become automatic, unconscious, and efficient when we do need to use those systems appropriately. 

With vision therapy, it kind of looks different depending on where you are in the practice. You do not have to be board certified to offer vision therapy but I would argue that if you see somebody who is board-certified, you can get a very similar variation among all of those practitioners of what's going on. Regarding how vision therapy is initiated and what that looks like, that's very dependent on the doctor's model of vision. For us, we put a huge emphasis on home therapy on top of office therapy where ideally, we're teaching skills in the office and then giving ways to practice those skills at home. The more somebody practices any newly learned skill, the faster it becomes habitual and learned. You can usually get success without home therapy but it's going to take longer. Hence, the more that we can get somebody's brain to engage in appropriate visual skills, visual abilities, and appropriate processing, the faster the program goes. 

As for how long it takes, I think it really does depend on the case, the frequency of learning, and what confounding variables are also in place. I would say with the right motivation and compliance, somebody should see changes in terms of symptoms within a couple weeks at the longest. With brain injury individuals, there's a little bit of a period of disequilibrium where we almost are forced to break down some bad habits before new or better ones are in place. So always ask the doctor that you're working with what to expect from a different time frame so that especially if it's predictable, you get a much better sense of how to prepare for life accordingly. 

Also, it's very easy to find somebody's threshold. We always want to stay below the threshold but push the patient enough that there's learning that takes place without overdoing it. I think as long as communication is open between the patient and the individuals providing the therapy for them, then it's a matter of just pushing them as hard as they allow it while still maintaining good progress. Going back to the initial example of the eyes pointing in different positions, if the brain is ignoring input from one eye completely, then in therapy we're going to first have to get the brain to know what the world looks like and feels like when they're not using their eyes together. Then, turn the information on from that eye so that the brain can receive both eyes’ information. That's also often going to create double vision and in the first session, there should be strategies taught and put in place to help learn how to eliminate double vision. 

I think oftentimes, you have to figure out what the maladaptations are and how to eliminate them first before things are perfect. However, there should definitely be consistent improvement and nutritional basis as well as other therapies should be involved as well. Very often, vision therapy is what raises the ceiling for a lot of other treatments. This is because it's tying together a lot of the work that's being tapped into from other treatments, where we're accessing so much of the brain that's either been bypassed or that's not really functioning at the moment.