During this live webinar, we discuss the role of using prism to alleviate diplopia. We will first describe the testing used to evaluate a diplopic patient. Next, we will use a step-wise approach to investigate the etiology of the double vision which will determine what type of prism to utilize. The advantages of permanent (ground-in), temporary (Fresnel) and occlusion will be addressed. Finally, cases will be used to illustrate how to prescribe prism for common neuro-ophthalmic and neurologic disorders including cranial nerve palsies, thyroid eye disease and neuro-degenerative disease.

Lecturer: Dr. Kelsey Moody Mileski, OD, FAAO, Emory Eye Center, USA

Transcript

DR MILESKI: Hello, everyone. So I am Dr. Mileski. And I am going to be giving our lecture today. Let me just get my screen up. All righty. So we’re gonna be talking today about prescribing prism for diplopia and neuro-ophthalmic disorders. I’m an optometrist at the Emory Eye Center. And I work with a lot of these patients in regards to their prism. I have no financial disclosures. And so when we think about double vision, we know that just to simply define it for our patients, it’s seeing two images of the same object. And this really can be for monocular reasons or potentially binocular reasons as well. And when we’re thinking about monocular reasons, we can think about simple things like refractive error. Is something coming from the cornea, the lens, or the retina, in and of itself? Potentially things like an epiretinal membrane, if there’s any swelling in the retina, anything that’s changing the location of the fovea. However, binocular diplopia is what we really want to focus on today. And what that really means is that you’re not bifoveal. You’re seeing two images of the same object. And so when we’re evaluating patients for double vision, our history is really the key to make sure that this is truly binocular diplopia and not monocular diplopia. And there are different questions that you can ask to try to address this. So specifically, if they cover either eye, does the double vision go away? So you want to ask not just about any eye, but specifically — do they cover their right eye, it goes away, and if they cover the left eye, it goes away. If they cover the right eye and it goes away, but they cover the left eye and it’s still present, that tells you there’s at least a monocular component coming from the right eye. You want to ask about direction. Are the images split side by side? Are they more at a diagonal, or are they separated up and down? This can help in your differential, what’s potentially causing the double vision so we can treat it. The duration. Has it been going on acutely, happened just in the past few days or weeks, or is it something that’s been present for several years and is maybe now getting more frequent? The location of the double vision. Is it just at distance? Is it when you’re reading? Is it when you look to the right? Again, this can give us a good hint to the etiology of the double vision. Any associated symptoms. Things like headache, eye pain, tearing, particularly in one eye, again, this can help with our differential, if potentially it’s coming from the orbit itself. And then any history of an eye turn or abnormal head posture. That can give us an idea if maybe this is more longstanding, and it’s just starting to decompensate at this point. And so we have different tools during our examination that can help us evaluate for the double vision. And the biggest thing is doing what’s called a dedicated motor examination. So first starting with just the sensory system, or the eye’s ability to have fusion. And we can do this typically in one of two ways. Either with a Worth 4 dot or Randot stereopsis. Personally, I prefer Worth 4 dot. I think it’s easier for the patient to understand. It’s something you can easily bring with you, if you’re doing examinations remotely. And it’s actually very cost effective, if you have to order this for yourself. It also is very good at giving you information at both distance and near, whereas Randot is very dependent on doing it at near, and the patient’s prescription being accurate. Where I find Worth 4 dot, that’s not necessarily as true. So with Worth 4 dot, you’re going to have a pair of glasses. Just like this. The right eye will have a red lens. The left eye will have a green lens. Because of that, you can even do that with a trial frame, with a red and green lens. The only thing you would necessarily have to purchase is the adapter here, which can be attached to a pen light, or there are also flashlights that have this as well. So the right eye will see red. The left eye will see green. So when this target is presented to the patient, if they have fusion, then they’ll see four dots. The right eye will see the red, the left will see the green, and the white dot can be red, green, or a mixture of the two. Sometimes patients will describe it as alternating between the two colors. Whereas if they are seeing double, they should see five dots. Where each eye will independently see the white dot. And if they have double vision where they have esotropia, where the eye is turning in, the red dots will be to the right of the green dots, which is called uncrossed diplopia. Whereas if they have an exotropia and the eye is out, the red dots will be to the left of the green dots. This gives you a really good gauge of potentially what the patient is describing. Also, the patient could be suppressing, even though they might tell you that they’re seeing diplopia. This is a good indication that this has been going on probably for a longer period of time. And in that case, they’re suppressing — if the right eye only sees two red dots, there’s no green, or the left eye sees two green dots and no red. After checking the sensory system, we’re now going to look at our motor system. And that first just entails looking at the extraocular motility, seeing how far out the eyes can move in all fields of gaze. Making sure you’re bringing the eye all the way out to the point where you ideally don’t see any sclera. If you see any evidence of sclera on the sides, that could be an indication that potentially there could be a mild deficit. And then to measure it, to give us kind of — telling us if it’s a phoria, is it a tropia, how the eye is turning, how frequently and to what magnitude, and looking for specific patterns of double vision, is the next thing and the most important thing we do. The first thing is the cover test. You can really do cover testing or a Maddox rod. Personally, I prefer cover tests, although I do have a lot of colleagues who prefer Maddox rod, so that’s really up to you, on what is ideal for your practice. This is just an illustration on how to properly do a cover test, in case it’s not something you do regularly. And you can start with a unilateral test, and that’s really going to tell you the direction and the duration of the eye turning. So is the eye turning in? Is it turning out? Up or down? And is it constant or intermittent? So you’re really going to just be covering one eye at a time, and then taking the paddle away, and after a few minutes, you can do the same thing for the fellow eye. Again, giving them a target at distance, and then you can also do this at near. For most of the things that we’re talking about for neuro-ophthalmic etiologies, most of it will be at distance, although there are a few things that are dedicated purely to near, so we want to check both. So what you’re going to do is cover the eye. And uncover it. And what you’re looking for is to see how the eye moves into the resting position. And so if the eye is turning in, when the eye is covered, it will naturally then turn in, and when you take the paddle away, you’ll want to refixate, and the eye will naturally move out. The opposite is true for exotropias. When the eye is covered, the eye will naturally rest out, and when you remove the paddle to find fixation, it will then move in. The same thing for vertical misalignment. So for hypertropias, the eye will rest up and come down to refixate. For hypertropias, the eye will rest down and come up to refixate. With hypertropias, I often call the hypertropic eye — so even though there might be a deficit in the left eye, if the left eye is down, I still sometimes will call it a right hypertropia. I find that the nomenclature just makes a little bit more sense. Although it can be called either way. So you’ll see that throughout the lecture. So again, we are going to cover the eye. The eye right now rests in, while it’s covered. I take the paddle away. It moves out. And because of that, that tells me that this is an esotropia. Now, here I’m covering the eye. The eye is naturally resting out. It comes back in. Refixation. It moves out. Comes back in to pick up refixation. So this is an exotropia. Same thing here. The eye moves up as it’s covered. It comes down. And that is left hypertropia, and then here I pull the paddle away, it comes up, it comes up, and so this is either a left hypotropia or a right hypertropia. With your unilateral cover test, if it’s a tropia, the eye will always be moving and coming back into fixation. Now, they can still have a phoria that can be large and can be causing double vision that you may not see if you’re just purely doing the unilateral cover test. The next is your alternating cover test. So this will tell you if they have a phoria, and the magnitude and the pattern. This is where we’re going to start to introduce the prism, to measure the magnitude, and we’re also gonna look at this in different directions of gaze to see if there’s any specific pattern that puts us towards a specific etiology for the double vision. And so here we’re going to cover the left eye. And we’re gonna quickly go back and forth between the right and left eyes. And here we’re seeing that as the eye is covered, it is moving out and it’s coming back in to pick up refixation. So this would be our exophoria. So now we’re going to introduce the prism to measure it. So we’re gonna introduce the prism. And we’re gonna start with a low number, and we’re gonna slowly start to bring the prism down, so we can start to neutralize the misalignment. With our goal being that we’re seeing little to no movement, or sometimes I even reverse the movement, so now I create an esotropia, and then I go backwards to make sure that it’s neutralized. That’s one way that you can check your measurement. And so when we think about what prism does, a prism is really a refracting lens that bends light. And so we use this in patients with double vision to move the image to where the eye is naturally resting. And so the image is going to move towards the apex or the points of the prism. And so to measure this, we want to put the apex of the prism where the eye is naturally resting. And so with that, this is all assuming right now for the right eye — for esotropias, we’re gonna put the base out. So that the point of the prism is resting towards the nose, where the eye is resting. Exotropias will be base in, hypertropias will be base down, and hypotropias will be base up. Now, if you put that over the left eye, it could potentially change in the direction I have the prism kind of resting right here. Whereas it will stay the same obviously for the vertical misalignment. So here with this patient we said they had an exophoria. We’re gonna introduce a prism. It’s going to be base in, because the eye is resting out. And I want to put the apex of the prism where the eye is located. We’re gonna move back and forth. It’s obviously not neutralized yet. We’re gonna move back and forth here. We’re getting closer. And we’re gonna move back and forth. We see no movement. And that would be what we record, as the magnitude of the deviation. We then want to do this in multiple positions of gaze, to look for a specific pattern. This is a patient who has a mild cranial nerve III palsy. You can see she has a ptosis on the right eye. The right eye doesn’t go up to the same degree as the left eye. So that would create a left hypertropia. As she looks down, you can see that the right eye doesn’t go all the way down. So now she has a right hypertropia. Which is called a reversing hyperdeviation, which is very pathognomonic for a cranial nerve III palsy. She also has a very mild adduction deficit here, although it’s difficult to see in this picture. And again, that’s very pathognomonic for a cranial nerve III palsy. Again, you’re looking for these patterns. That’s what we want to do next. And we’re only going to do that with an alternating cover test. When you’re looking for these patterns in different positions of gaze, really doing a unilateral cover test doesn’t give you any useful information. So just an alternating cover test here. We can do the same thing with a Maddox rod. However, this is now going to create a subjective component to the test. Whereas a cover test is really going to give you just objective measures. So here we really need the patient to be able to be a big communicator. Sometimes I find with certain patients this can be difficult for them to understand. Specifically what I’m asking. But it can give you a good quick sense of what a pattern is, without taking a measurement, or you can also introduce prism to get a measurement as well. And so with this test you’re going to present a pen light, and then the patient is going to hold a red lens that has lines on it. And the lines can be oriented either horizontally or vertically. When the lines are horizontal, like in this picture here, it then creates a vertical image, and this is going to let you take a measurement for horizontal deviations. So just think — if the lines are horizontally oriented, it’s gonna be for horizontal measurements. And so what the patient will see is a red vertical line. And then the white light from the pen light. If a patient has an orthophoria or no deviation, then the red line should bisect the white light. And that’s really what you’re looking for, if you’re then going to introduce a prism bar, to create it to be neutral. However, even if a patient has a mild phoria that they’re asymptomatic for, they can still have a mild separation, like we see here. This is as the patient’s viewing this. And so the red line is to the right of the white light. Which the red Maddox rod is placed over the right eye. So this is uncrossed, meaning there’s an esophoria or tropia. You really can’t assess that with a Maddox rod. And that’s where I find patients have the biggest confusion, telling me what’s to the right and what’s to the left. So that’s something to take into consideration with it, although it still is a useful and quick test, potentially. The same thing can be done for vertical deviations. However, now we’re going to flip our lines, so now we’re going to orient the lines vertically, so that we’re measuring vertical deviations. But the patient will now see a horizontal line. And again, our endpoint is having this horizontal line bisect the white light. Similar to exotropias, hypertropias will be reversed. Meaning if the patient sees the red line below the white light, then that’s indicating that they have a right hypertropia. And again, we can introduce prism to give us neutrality. The other things that we want to consider in addition to our basic sensorimotor examination is looking at things like exophthalmometry, is one eye more proptotic than the other eye, that can tell us that something is localizing to the orbit, the etiology — look at the lids, could there potentially be a Horner syndrome associated with it, could this be evidence of a cranial nerve III palsy, and if you specifically have a vertical deviation, you may want to do a double Maddox rod, similar to what we talked about with the cover test type of Maddox rod, but here you’re going to present the patient with two Maddox rod lenses, and this can be very helpful to evaluate for torsion, and help you look for differences between a cranial nerve IV palsy and a skew deviation. More information from more of a diagnostics purpose, not so much for helping with the prism, but it really can help you try to differentiate between these two etiologies. So when it comes to treating double vision, the first and most important thing is to rule out a pathological cause. That can be with neuroimaging or bloodwork. This may have already been investigated, and this patient is then getting referred to you for prism, but this is always something you want to make sure was addressed. Specifically if you’re doing your cover test and you’re finding a pattern that can be concerning for a specific neuro-ophthalmic etiology. And the next things to think about are surgical causes and non-surgical causes. For this part of the discussion today, we’re really going to be emphasizing non-surgical causes here. When we think about non-surgical causes, we’re going to think about prism not just for measuring misalignment, but also for treating it. It can be done in two ways. With Fresnel prism, which is a temporary fix, although it can be permanent for some patients as well, and ground in prism. Another important thing to consider is occlusion, because that can be a better option for some people. This can be your traditional patching or putting on a patient’s glasses in what’s called a Bangerter foil. This can be a temporary thing. The patient can try it. It’s a filter that gets placed on the surface of the glass. It can be ordered in different densities, so it can be just a very mild clouding. You can see it here. Where the lens looks fogged. It could be just 20/40, 20/60, so it gives them mild blur. However, I find that 2400 to light perception typically gives patients the best result, because it’s going to create enough blur so that they don’t see double, but it still lets them get light to the eye, which a lot of patients find to be a little bit more comfortable than completely patching the eye itself. If they like this, you can even then order the glasses fogged, so that you don’t have this actual film on the glass. Temporarily, if this isn’t accessible to you, tape actually does a very similar thing, although cosmetically, it doesn’t look as good as fogging the lens or putting this Bangerter foil on it. So our goal with prism is to create binocular vision in primary gaze, meaning when the patient looks straight ahead. This means that potentially when they look to the right or left, they may still be diplopic. So potentially telling them that they may need to move their eye to the side. Our goal is always straight ahead for reading. We want to put the apex of the prism, the point where the eye is resting — so for exotropias, we’re going to prescribe base-in prism. For esotropias, we’re going to prescribe base-out prism. For hypertropias, base-down prism, and hypotropias, base-up prism. And potentially these patients may need two pairs of glasses, if their deviation is different at both distance and near. Because of this, I often take patients out of progressives and bifocals, if they need prism. If they need a higher amount of prism, I always take them out of a progressive, even if their deviation is equal at distance and near. I find the progressives just end up causing too much discomfort from a visual standpoint, but also they’re not looking through the appropriate amount of prism, just from the progressive design. It’s not very successful, typically. Small amounts of prism, I can sometimes do it. But most of the time, we typically want to take them out of progressives. And so we’re gonna start with Fresnel prisms. So a Fresnel prism is a press-on lens that’s going to help alleviate the double vision. It’s typically used initially to determine if a patient can adapt to prism in general. Or if we really don’t know what the etiology is still. Because their alignment can potentially change. If it’s a vasculopathic etiology, we know it can get better over a few weeks to months, so we might have to change out the prism, which is very easy to do if we have a Fresnel lens. Or potentially we don’t know what’s causing the double vision. It might end up being myasthenia gravis. It would be really unfortunate if a patient paid money to get ground-in prism. That’s not gonna work for them. Oftentimes too we find a neurologic cause for the prism, and so that’s going to be subject to change. For all those reasons, we don’t want to go with ground-in prism right away, if we don’t know what’s causing it and we don’t know if it’s stable. The advantage to Fresnel prism is it can be put on the glasses immediately for relief. Assuming you have a stack of prisms to try with the patient. That’s really what I recommend. Keeping two to three of each type of Fresnel in your office, if that’s available to you, because then you can try them on with the patient in the clinic, cut it yourself, which is much easier than having the patient cut it on their own, and then it’s something you can give your patients right away. But I always like to try them in the clinic, because it gives me a better idea of what they would like, because it can be a little bit different than sometimes what you expect. Specifically because of the blur that it causes. Again, it’s easy to change these lenses out. Oftentimes with patients who I think they’re gonna start improving — maybe they have a traumatic 6 or 4, and we think this might get better with time, I bring them back every 4 to 6 weeks and sometimes we change out their Fresnel. It’s lightweight, so if we have to go to higher values, so we can prescribe up to 40 prism diopters of a Fresnel prism — it’s not gonna be very heavy. So that’s a great thing to think about. And it’s inexpensive. One important thing to note about Fresnel prisms is when I’m using it to treat double vision, I only put it in front of one eye, because it creates a natural blurry image, because of the lines that are on the glass. And so if we put it in front of both eyes, these patients are gonna be very uncomfortable. So you only ever want to put this in front of one eye, whereas ground-in prism we split. So again, only in front of one eye. I always tell the patient that it’s gonna be blurry in front of that eye, especially if they close that eye. When they’re driving, they’re gonna get a lot of glare off of headlights, because it’s basically creating this distortion, naturally. It is visible. So other people are going to see the prism. Which some people really don’t like. And it’s hard, although possible, to correct both horizontal and vertical deviation simultaneously. What I often find is that if you are correcting the larger deviation, sometimes patients, because of that blur, aren’t that symptomatic for the vertical misalignment. However, you can rotate the Fresnel to try to correct for both. There are mathematical models that can help you do this. Although I find that just doing it with the patient in the room is honestly probably the most helpful way to determine what power and how much rotation you’ll need. And so I saw some of the questions from before about how to cut a Fresnel. So I’m gonna demonstrate this here. And so I’ll kind of talk you through it. This is what the Fresnel prism is going to look like. And the first thing that I’m doing is trying to figure out the way that the lens is — that the Fresnel is oriented. So where the prism is. And so personally, I just like to run my finger along the edge, and try to find where the base is. Obviously my nail will kind of get stuck when it hits the prism, whereas the other way, you can easily kind of run your finger across it, and it should be smooth. There’s a rough side of the Fresnel. And a smooth side on the opposite side. The smooth side is what we’re gonna physically put onto the lens. The rough side is gonna give you the outside. So first we’ll find the orientation of the prism. I can see here, it’s gonna be oriented base out, we’re gonna be correcting esotropia here, and you can see here how then it shifts the image. And so again, I’m just gonna confirm the way that it’s oriented. I always like to start at the edge, because potentially you can reuse the prism. Which can then be very helpful for your patients, even from a billing standpoint, of — you can use a prism potentially for two patients. And so I’m making sure that the lines are perfectly straight up and down at this point. I’m putting it down on a hard surface. I’m doing this from home. So typically I’m gonna put it on something a little bit cleaner, clean the lens as well, and use a marker or pen to trace out the glass. Again, the smooth side right now is on the lens. And I always put these on the inside of the patient’s glasses. I find that it keeps the prism a little bit cleaner than if it were on the outside. It also keeps it to stay on a little bit better. And then I’m going to now cut the prism. And I typically try to cut inside of my line, so that you’re not gonna see that marker. And it’s better actually for the prism to be a little bit smaller than the frame. Than to be a little bit bigger. If it’s not on the lens in one location, it’s getting lifted by the edge of the frame, that prism is gonna come right off. It’s gonna get dirty really quickly. So I much prefer a prism that’s going to be smaller than bigger, and that lets the patient potentially take it off to clean easier. So I like to leave a little nook potentially right here in the corner, so that the patient can easily take it off. So here I see that there’s a loose edge. And so I’m going to take it off. And I’m going to trim it in that area as well. And then put it on the inside of the lens. Make sure there’s no loose edges. Again, make sure the lenses are straight up and down. And then just smooth it out onto the lens, to try to get out the bubbles, which can sometimes be the hardest part. And you can see here I have — this is a 20, actually. So that’s fairly high. And it’s really not that cosmetically noticeable on the glass. The glass maybe looks a little bit dirty. But in general, it’s not creating this terrible cosmetic look, although it is more noticeable than if you had ground-in prism. And so for ground-in prism, this is really going to be now built into the glasses prescription. So you definitely have to have an updated refraction, if you’re going to be giving a patient ground-in prism. This is great to use when you know that the deviation is stable, or you know what’s causing the double vision. And so the advantage to this is you’re now gonna have two clear lenses. There’s going to be nothing on the surface of the glass. And it can be split between the right and the left eye, to make the glasses appear symmetric. So I always split my prism. So if I’m prescribing 10 base-in prism, I’m gonna put 5 in the right eye, 5 in the left eye. The only time that I consider not putting them equal — let’s say the patient is very myopic in one eye, they’re a -5 in the right eye and only a -1 in the left eye, I may want to put more prism in the left eye, and occasionally I’ll put that to the recommendation of the optical, what would be the best to make the glasses look symmetric, because they can run better calculations within their labs themselves. Another advantage is it’s not easily visible to other people. So oftentimes from a cosmetic standpoint, patients prefer this, because people won’t know they have prism in their glasses, unless it’s very, very thick, and it easily corrects horizontal and vertical deviations. I can put 5 base prism in the left eye and 3 base down, and it’s not going to be difficult for that. We can really kind of demonstrate this just even in the clinic, by putting this in a trial frame. It will give the same effect. Again, this is better doing it in a single lens and not potentially doing it in a progressive. It’s much more successful when we think about it that way. The biggest disadvantage is I can really typically put only 20 prism diopters, 10 in each eye. That’s still pretty eye. Some labs don’t prefer putting that high of an amount. Some labs only prefer up to 6 to 8 in each eye independently. So there is a max amount of prism I can put in the glass. It does take some time to be made. Typically longer than what it would be without prism. And it can be very expensive. Here at least it’s typically about $10 per diopter of prism. So if I’m putting 20 prism diopters in a glass, that’s an extra $200 to the patient. Again, that’s a rough estimate. Every optical obviously is going to be different. But it definitely adds a cost to the patient. And they may also need multiple changes to the glasses. I always bring these patients back, because sometimes what we get in the exam room doesn’t correlate to what they need in real life, and we might need to make a change. And because of that, you always need to bring these patients back in about 4 to 6 weeks, so you can readdress that. Occlusion is something I still want to mention, because it sometimes is the best option, and that’s okay, if occlusion is the best option. Our goal is to create with occlusion monocular vision to alleviate double vision. That’s obviously not ideal, because you’re then going to lose binocular vision. It also cosmetically sometimes isn’t an ideal option. However, some patients are very, very sensitive to the fact that they may be asymptomatic in primary gaze, but when they move their eyes in any other direction, they’re going to have double vision, and it can be very bothersome. And so because of that, sometimes they prefer to be occluded. Also they don’t need additional glasses. Sometimes you can even do this with a contact lens, which can be cosmetically an advantage, and it also gives them immediate relief and is inexpensive. So it’s still something to always think about in the acute stage, but sometimes even in the chronic stage as well. So when we’re thinking about double vision, we want to think about our differential. And so we’re gonna start purely here with just our muscles. So with this superior rectus, it’s gonna elevate the eye, intort the eye, and adduct the eye. The medial rectus is going to be purely adduction. The inferior rectus is going to do depression, extorsion, and a little bit of adduction in the tertiary action as well. And the inferior oblique is going to create extorsion, depression, and abduction. The lateral rectus, pure abduction. Only a primary action. And the superior oblique is going to create intorsion, depression, and abduction. And so if we have a deficit here in one of the cranial nerves, these are the things that we can expect. So for a cranial nerve III palsy, similar to that picture that I showed you before, we’re going to have a lack of elevation and depression, adduction, and then they may also have a ptosis, because cranial nerve III innervates the levator, and the pupil may be big, because it naturally creates constriction of the pupil. For a cranial nerve IV palsy, because the superior oblique does intorsion, depression, and abduction, these patients typically have a hypertropia in that eye that gets worse when they abduct, and they also then will have excyclotorsion of the eye. That’s how you can differentiate it from a skew deviation. For cranial nerve VI palsy, this is probably the thing people see the most often. It’s gonna be purely a lack of abduction. Doesn’t have to be zero. Sometimes it can be a 25%, 20% deficit, and you can still have symptoms. The next thing to always think about is a deficit of the neuromuscular junction. So where the nerve is sending a signal to the muscle. And that’s what we typically see in patients with myasthenia gravis. Sometimes these patients have double vision that’s worse at the end of the day, it can be very variable, it can change direction, sometimes it’s horizontal, sometimes it’s vertical. And typically these patients are not good candidates for prism, because it can change. One minute you check the patient’s deviation, they leave, they go home, and the deviation can be completely different. So often occlusion is a better option for these patients. Sometimes when these patients are treated, their double vision can go away. And very rarely, I’ve seen patients who are treated and controlled, and have a stable deviation, and in those cases, you can potentially consider starting with a Fresnel, although it’s definitely — doesn’t happen as often as we would like. And then finally, different causes that can deal with the brain. Typically we think brain stem in general. That’s where all the cranial nerves that are gonna innervate our muscles are starting. However, it can happen with any of the pathways, even sharing information with the brain stem as well. And so these are our big things on our differential. And I’m not gonna go into these to the same degree, since we’re purely talking more so about treatment. But looking for things like internuclear ophthalmoplegia, these patients will have an adduction deficit, they’ll have exotropia, they’ll need base-in prism, gaze palsy, where they won’t be able to move the eye, a skew deviation, they’ll have a hyper, but the eye will be incyclotorted instead of excyclotorted, dorsal midbrain syndrome, deficit in vertical eye movements, or neurodegenerative disease. This is a lot of patients I see as well. Different things like Parkinson’s and progressive supranuclear palsy, they often have convergence insufficiency and need prism at near to read comfortably. Obviously cranial nerve palsies we want to think about, IV and VI, myasthenia gravis, as we mentioned, and something purely localizing to the muscle itself. So when we’re treating neurologic conditions with prism, like I said, we always want to make sure the etiology is known or under investigation. We then want to update their refraction at both distance and near, specifically like I said, we may need two pairs of glasses, we want to do a cover test or a Maddox rod without any prescription, at distance and all positions of gaze. Which means you may have to create a big target to be able to do this, if the patient has a high prescription. Occasionally I even put a white dot on a black background to be able to do this. We don’t want them to have their glasses on, because if they turn their head to do this with the glasses on, they’re gonna get an induced prism effect from the glasses themselves. We want to do a cover test at distance and near with glasses prescription on, which can be done with a trial frame or potentially using the patient’s current glasses, and want to trial prism at both distance and near. For horizontal prism, we’re going to start with typically about half of their objective measurement. And then we’re gonna move the bar up until we get fusion. And so the prism can be placed over either eye. So let’s say for example I have — I measure 16 prism diopters. I typically start with an 8. And I present a horizontal line for the patient and see if they have fusion, or if they’re still diplopic. It can be placed over either eye. The only time I put it over the paretic eye is if I’m putting the patient in a position of gaze where they can’t move the eye to. Let’s say the patient can’t abduct and I’m having the patient turn their head. I’m going to want to put the prism over the left eye here, so I can already move the image to where the eye is before I check the measurement. Otherwise you’re not gonna see any movement. You then want to move the bar up and down by about two prism diopters once you get fusion to see when it breaks or when it starts to become blurry to the patient. Sometimes they get blur before it breaks into diplopia. And that median point is typically my endpoint, and I want to recheck their fusion to see if they see four dots on the four dot test. For vertical prism, the biggest difference is I actually start with my objective measurement, because typically there isn’t this compensatory movement that patients can create. To be comfortable. And so I typically start with what I objectively measure. Again, it can be placed over either eye, and I’m gonna move the bar up and down by 1 to 2 prism diopters until the fusion breaks and the median point is going to be my endpoint, and I’m gonna recheck the fusion. Sometimes with vertical deviations I like to trial frame them, because I can make even a half a prism diopter change, whereas if I use the bar, sometimes I have to move it by 2, and that’s too much. When we’re trying to combine prism for horizontal and vertical, you want to always neutralize the larger deviation first. So if your patient has a 20 exotropia and a 5 hyper, neutralize the 20 first and then start to incorporate the vertical prism after. Sometimes I’ll try to move the images until they are lined up in one direction. And so if I want to neutralize my horizontal deviation first, I’m gonna try to make the images so that they’re right on top of each other, and then try to introduce the vertical prism overtop, and you may have to start to tweak it. Oftentimes you may need two hands to do this, or you can do it in a trial frame, like I said. Sometimes that can be easier. Specifically when you’re doing two different types of prism at the same time, it can be very time-consuming. And challenging. With variable results. But it is obtainable. You just have to take your time to do this. So when we’re starting to think about prisms, like I said, we’re gonna potentially do Fresnel prism first. Specifically if the etiology is unknown. And if the deviation may change. Then we’ll consider ground-in prism, specifically if after we know the etiology, if any deficit remains or we know that it’s stable or we know the cause. And we’ll consider referral for surgical intervention potentially, if patients are interested in this. So when do we refer for surgery? So I usually refer for patients who have constant diplopia. And their cover testing has been stable for about a year. If we get to six months, you can think about putting the referral in at that point, because it may take time to get in with your surgeon, and you may want to evaluate them, but typically most surgeons won’t do surgery until about a year that things have been stable. Also when I know it’s not going to progress anymore. Potentially this patient had a cranial nerve III palsy, and it’s been stable for a long period of time, and they’re not undergoing any treatment for it at this point. If they’re able to achieve fusion with prism — this is very important. If you cannot get your patient to fuse with prism, they probably won’t fuse with surgery. Because really with prism, instead of moving the image to where the eye is located, we’re really now moving the eye to where the image is. So it’s still doing a similar thing. And if we can’t get fusion with prism, it really won’t be able to happen with surgery either. And so that is really one thing that’s always important to remember. Similar to prism, the goal is gonna be single vision in primary gaze. They may still be diplopic in other gazes, so you want to make sure they’re aware of that. That can be one thing they’re hesitant about with surgery. They’re not gonna be perfect in all positions of gaze. But from a cosmetic and glasses standpoint, this is a good option, so I always talk to them about surgery if they’re a good candidate. Also you want to make sure their deviation is large enough for surgery. So in general, for hypertropias, most surgeons won’t do surgery unless it’s about 5 to 6 prism diopters or larger. And the same thing for horizontal measurements. Typically, 8 to 10 prism diopters or larger they’ll do surgery. Anything less, the room for error is too great, and they typically do not operate on those patients. So you also want to make sure the measurement is big enough for them to be a surgical candidate. So I saw also a lot of questions about yoked prism. For me, I see most patients with double vision. So I often don’t do yoked prism for hemianopsias. Some of my low vision colleagues do. So it’s something to consider. Oftentimes we think about it for nystagmus. Sometimes I see patients in regards to that, to try to yoke them out of their position of the nystagmus. Or an abnormal head posture. An important thing to remember, though, is that a 2 diopter prism only shifts the image by 1 degree. And so you really need a lot of prism to move the image. In both directions. And what a yoked prism is, for some people who may not know that, is putting the prism in the same direction in both eyes to move the image. If you want to move the image up, based on prism, it’ll shift the prism up. For visual field defects, you want to put the prism in the base, in the direction of the defect, so it shifts the prism out of the visual field defect. But again, if you’re doing this in ground-in glasses, you’re gonna shift everything and you really can only put 20 prism diopters. You’re only gonna shift the field by about 10 degrees. You can put higher amounts with Fresnel prism, however, it will require two in front of each eye, which will acquire blur and distortion, and because of that, it’s better to place it sectorally, like this image here, so the patient can look straight ahead, but move to the area of their defect to shift the image to the side. This can be done with sectoral prism or the Peli lens. You need a good rehab team to work with to be successful in this. It also can be used in visual neglect. We see this commonly after right brain stroke and when patients will ignore the left side. You may also see they have this compensatory head turn to the right, because they’re going to be neglecting the left side. And we see commonly that patients have an extinction phenomenon with visual neglect where if you present a stimulus on the right side and the left side, they’ll ignore the image on the left side, so prism adaption can be used with these patients with yoked prism. Typically we yoke the prism to the right, and the patient will then perform finger to nose exercises, basically. And what you’ll find is that they’ll overcompensate to the right, because the prism is in place, and then with time, as they’re doing it, they’ll start to adapt to move to the left, to make up for that. Now, when the prism is removed, they’ll naturally overcorrect to the left, and that will help them start to be aware of the field to the left side. Typically it takes about 10 to 20 treatments for them to have any benefit. Again, done in the acute phase, in the rehab setting. The biggest challenges otherwise we see with prism are: If there’s other ocular comorbidities, like maculopathies, this can again change the fovea, in one eye. So what you actually measure can be different than what the patient subjectively likes. If there’s asymmetric acuities, we might have a clear image in one eye, so they’re 20/20. If the other eye is 20/70 with an epiretinal membrane and there’s distortion, I’m now trying to put a clear image on top of a blurry image. And that might not be ideal for the patient. Sometimes that just creates a blurry image. So that can definitely be a challenge. In patients who have other visual field defects, whether it be homonymous or they consider glaucoma, a dense inferior arcuate, sometimes if I’m moving the prism I can move them into the defect and they end up suppressing. That can be advantageous or can be a disadvantage. It really depends on what the patient’s goal is. So that can definitely become a challenge. A big challenge I see is patients not wanting to come out of their progressive glasses or have two separate glasses, because it can be challenging to them. Typically it’s the biggest complaint I have for patients. Specifically when they go to the grocery store, they have to change their glasses and it’s really cumbersome. But sometimes I’ll let them try doing it in a progressive and nine times out of ten it’s unsuccessful, and they end up going back to the two pairs of glasses. Another problem is if they need more than 40 diopters of prism. Sometimes patients with traumatic VIs, where they need 50 or 60 prism diopters. Sometimes I’ll give them ground-in prism so I can successfully put a Fresnel overtop of them. That’s usually the route I go, but sometimes occlusion is a better option. Nystagmus can be a problem, specifically if it’s in primary gaze, because I’ll have a shaky image that I’m trying to put over another image, which can create a lot of blur. And then if the patient is suppressing. Sometimes patients are suppressing and getting intermittent diplopia, and that can have a really hard time with fusion when that occurs. Those patients can be very challenging and time-consuming. We can occasionally get to an endpoint, but sometimes it’s okay to let them suppress as well. So let’s just go through a couple cases here for the next five minutes. So that we can then get to some of the questions. And so we have a 54-year-old male who is complaining of blurry vision and eye fatigue for two and a half years. He’s been noticing gradual blurry vision with driving and looking to the left. He notices some double vision when he’s turning his face to shave, both with and without glasses on. Ocular history is remarkable just for myopia, he has high cholesterol and depression and takes medications for that. He has no allergies and is a current smoker. On examination, he’s 20/25 in the right eye, 20/20 in the left, myopic and presbyopic, does correct to 20/20, pupils are normal. Everything else is normal. Normal pressures. Mildly proptotic, but equal between the two eyes and normal for his ethnicity, and anterior and posterior segment is unremarkable. However, when you look at extraocular motility, he has a mild left abduction deficit. When you present the Worth four dot, he has diplopia. He sees five dots total. Two red and three green. You cover test at near and distance with glasses on. He has a esotropia at distance and esophoria at near. At multiple positions of gaze, alternating, he has 12 esophoria that goes away when he looks to the right and increases to 25 when he looks to the left. So he has a left abduction deficit, broad differential. Cranial nerve VI palsy, myasthenia gravis, it’s variable, thyroid eye disease, essentially something in the orbit, or even twain’s retraction. The good thing is that it’s isolated, no fatigability, and it’s been a gradual change over the last two and a half years. So we’re gonna do a poll here. What type of prism at this point would you like to prescribe for this patient? So we have base-in Fresnel prism, base-out Fresnel prism, base-in ground-in prism and base-out ground-in prism. All right. So most of you would like to prescribe base-out Fresnel prism, and I agree with that. Fresnel prism is definitely the best option because we don’t know the cause. We definitely want to stick with Fresnel and we said he’s an eso deviation. The eye is resting in. So you want to put the apex where the eye is. That means it’s gonna be that triangle. So the base or the edge of the prism will be out. So we started with 6 base-out prism. Still diplopic. I measured a 12, started with 6, half of what I measured, so I increased to 10 to obtain fusion, moved the bar another 2, had improved clarity when I went to 12, but it was blurry when I increased to 14, so I stuck with 12 base-out prism and applied as Fresnel. This is a temporary fix. He was able to tolerate it at near, so we were able to do it on his regular glasses, and an MRI was ordered to determine etiology. Here he had a small meningioma. So the 6 is going to exit here, hit this meningioma, and it was the cause of his double vision. He came back, already saw neurosurgery, wanted to monitor with MRI, not interested in radiotherapy. However, he was bothered by the cosmesis of the Fresnel and requested ground-in prism. I rechecked his measurements. At this point, he was stable, so we educated him that it could change, but he still wanted to do ground-in prism so we created his regular glasses prism with 12 ground-in, split. At his follow-up visit, he had worsening diplopia, increased left abduction deficit, and when we recheck his measurement, he is now at 25 esotropia, compared to his original 12. And so at this point, we fit him with a 20 Fresnel over his 12, to give him a temporary fix. He was able to tolerate this at distance. He was gonna take his glasses off because he was myopic for reading, we sent him to radiation oncology to get treatment, because he had progression. He came back four months later, finished radiation a month ago, was hopeful to do ground-in prism, took off the Fresnel because he didn’t like the way it looked, even though he was diplopic. He was turning his head instead. We measured 18, less than before, and he really needed 24, which was too much to put in the glass. 20 was our typical max. He was very interested in surgery. We told him the surgeon probably wasn’t going to do anything at this point. But he was very adamant to be referred for surgery. We sent him to the surgeon, followed up with the surgeon, measurements were stable, but was going to wait several months before he considered surgery in this patient. I’m gonna do one more case here. So we have a 72-year-old male who is complaining of blurry vision in the right and left eye. He notes a hard time specifically looking up and down, has a hard time reading small print like the newspaper. Also has a hard time seeing the TV controls on his remote. And has now gone through multiple pairs of glasses without improvement. And currently wearing progressives. His ocular history — he has cataracts and dry eye, he’s not taking any eye drops, systemic history — has arthritis, atrial fibrillation, high blood pressure, high cholesterol, sleep apnea, and progressive supranuclear palsy, which is a neurodegenerative disease. He takes medications for those conditions. No allergies to medications. And the rest of his history is really unremarkable for what we’re talking about here. Best corrected acuity — he is 20/20 in both eyes, pupils are normal, as are confrontation fields, motility is restricted. We’ll show you that in a minute. Eye pressure is normal and reduced near point convergence at 20 centimeters. When we look at motility, he has both a supraduction and infraduction as well as abduction and adduction deficit. This is common in patients with supranuclear palsy. They have this vertical gaze palsy and a hard time moving the eyes in general. He has a 6 exophoria, and 18 exotropia. Anterior segment examination — he has dry eye, similar to Parkinson’s. We see these patients blink less often. So they can have a monocular component to their double vision as well. We want to make sure we treat the ocular surface as well as giving them prism. We’re gonna do another poll here. We have a patient with convergence insufficiency in the setting of supranuclear palsy. What type of prism would you like to prescribe? Just a reminder. He has an exotropia. So base-in Fresnel, base-out Fresnel, base-in ground-in prism or base-out ground-in prism. All right. So the consensus was base-in Fresnel prism. Base-in ground-in was second. Because we know what caused his deviation, we know he has progressive supranuclear palsy, I gave him base-in. So I updated his glasses prescription, and trial framed his near prescription, because that’s where he was symptomatic and where he had diplopia. Just to remind myself — he measured 18 exotropia. I started with 10 base-in at near. Still diplopic. Very common in patients with neurodegenerative disease. Often we have to give them a little bit more prism. I increased to 18, he had fusion, and it was blurrier when I decreased to 12 and 16, so we ended up sticking with 14 base-in prism. He has an infraduction deficit in both eyes, so I tried to yoke the prism as well. Giving him horizontal and introducing two vertical prism bars to yoke the material up, since he could not move his eyes down to be able to see it, but again, I would have to yoke it too much to get again — I could probably only get it at 20 degrees up, and I really needed to bring it up significantly more than that, for him to see in a normal range. So he did not respond to yoked prism. I also tried a little bit of prism at distance, just because he did have a moderate exophoria, but he didn’t notice it was more comfortable or clearer. I took him out of progressives. That was his biggest issue. He couldn’t move his eyes down to even use the progressive. So we were gonna fit him with near vision only glasses with ground-in prism. I started with a 14, also wanted him to hold his reading material higher, or if it ever became difficult for him to get different visual aids to bring his visual material higher, like a reading stand or even just elevating things. This is what I tell patients even with progressive supranuclear palsy when they’re eating. It’s helpful to elevate the food on some sort of surface. I prescribed him a separate pair of distance glasses without prism and brought him back in four weeks. I’m gonna skip this case just so we have time for questions, because it really just talks about occlusion. So in general, prism can be challenging and time-consuming. And so you really want to make sure you’re scheduling appropriate time slots. Often these patients need about 45 minutes to an hour. Maybe 30 minutes for a follow-up. You want to make sure that a neuro-ophthalmic etiology has been worked up. Either by yourself or by the referring provider. And if you see something that seems to be different than what the provider got you, you want to make sure that’s always getting addressed first, because sometimes this can be a life threatening condition. You want to always set patients’ expectations for prism. When I see them for the first time, I tell them that prism does not work for everybody, and specifically if they have other ocular comorbidities that can make it more challenging, it can be successful in only certain positions of gaze so they know what to expect. I bring them back for follow-up in 4 to 6 weeks, to make sure the glasses were made correctly, I always read them myself, and don’t be afraid to make changes to the glasses. Sometimes I need to increase prism, so I issue them a doctor’s remake, bring them back in that shorter window of time, so they can go back to the optical and get it remade where there’s not a charge to them from the optical. It’s true in the US. I don’t know from an international standpoint how that works. But that’s always something to consider. I tell people from the beginning we might have to change the glasses. It might not be successful in your normal activities. And it’s sometimes okay to recommend occlusion. If you can’t get your patient comfortable with prism, if you can’t get them to fuse, if they’re too uncomfortable when they look in different directions of gaze, occlusion is an okay option. It can be a patch, it can be a foil, to get them sunlight to the eye, or if they’re really bothered by the cosmesis of that, pupil blocking contact lens can be a great option for people, or sometimes a high plus lens so they still get some light to the eye can do a similar thing. All right. So let’s look over some of the questions here. Okay. So I’m gonna start from the top here. And if anything got addressed in the lecture, I might just skip over it. So can prisms be prescribed in progressives? They can, but if I do it, I usually do it in very low amounts. 2 to 3 prism diopters. I often find that any higher amount patients are very uncomfortable, or they’re not looking through the appropriate amount. If a patient is adamant about trying a progressive, I usually caution them that it’s probably not going to work, but if they really want to try it, we can do it. Typically nine times out of ten we have to remake the glasses. How do you prescribe prisms for vertical and horizontal? As I said in the lecture, typically this works a little bit better with ground-in prism. I’m gonna trial frame them first in the room and we can potentially build it into the glasses. With Fresnels, we have to rotate the prism, which can sometimes be successful. Sometimes it’s not successful. So something we can always think about. I prefer to name the tropia by the tropic eye rather than always naming the hyper eye. I think that’s fine. It’s gonna be whatever you prefer. How do you address a patient if there’s a difference between distance and near? Two pairs of glasses, always. Is double vision examination — how useful is lid evaluation? It’s typically more so if you don’t know the cause. So if you’re looking to see if there’s any associated symptoms, that can help you determine what the etiology could be. Specifically cranial nerve III palsies or associated Horner syndrome. That can help you localize along the pathway of the extraocular — the nerves where the deficit might be. How can you say which eye has torsional deviation with Maddox rod? So you’re gonna — it’s better for double Maddox rod. So let’s say your patient has a right hypertropia. I always refer to the hypertropic eye, so when I’m doing double Maddox rod, I’m gonna cover the one eye and rotate the Maddox rod to see where it lines up and see if the eye is intorted or excyclotorted. I do it based on that. If the eye is excyclotorted, that’s a skew deviation. If both eyes have the torsion in the same direction, it’s typically bilateral. Maximum ground-in prism, 20 prism diopters, how do we prescribe ground-in — vertical which is incomitant? So again, typically I said I do just primary gaze. So distance I’m gonna give them primary gaze. And reading if they’re looking down, I’m gonna take that measurement and have them hold their reading material where they typically would, and then I’m gonna give them that prism. So I educate them that if they move their eyes, that they may still be diplopic. Unfortunately there’s not a good lens like a progressive that can create a gradual change in the prism. That hopefully will be something that will be invented or created. But right now, that’s not a good option for people. Both horizontal — I think we addressed that question already. Can you explain how to differentiate cranial nerve IV and skew. I was just briefly doing that. Again, you’re gonna look at the hyper eye. Gonna have the patient turn the Maddox rod until it creates for them a vertical — line up and down or side by side. You can decide. And then you’re going to look to see if you’re doing a right eye, and a horizontal, if it’s turned in, and that’s telling you it’s intorsion, which is going to be a skew. If it’s out, that’s going to be a 4. I personally don’t use the Tangelini test for diplopia. I know some people do, but I don’t do that in my practice. Frequency for prism for phoria? Typically I see it in decompensated phorias where they have some control. A decent amount. Not all patients have neurologic etiologies. Sometimes they get referred to the neuro-ophthalmic clinic and it can be decompensated phoria. It’s not the majority of my patients, but it’s about 10%, 15%. I’m not quite sure what that question is. Fresnel with bifocal? You can. Putting it on the inside of the glass is better, because the lip of the bifocal can sometimes cause the Fresnel to lift up. But you want to make sure they’re comfortable at distance and near with it. Otherwise sometimes if it’s just distance, I cut just the top of the glass, if they’re okay with the image jump when they look down. That’s why it can be advantageous to do it in your exam room. Fresnel and Bangerter foil are more comfortable for patients if placed on the non-dominant eye. Very true. Good point. Often I demonstrate the Fresnel over both eyes, to see which they prefer having it over. Sometimes if they have a big restriction I’ll put it over the paretic eye so their field of vision is a little bit better. But I typically demonstrate it over both eyes to see which eye they feel more comfortable in. That’s a great point. Removing the lens and using a razor blade to cut the Fresnel makes a beautiful edge. I agree if you have that available to you. I usually only have scissors in my clinic, but potentially cutting with a razor is gonna make it a little bit better. Base are — image shifts up? Sometimes with low prism, the diopters, it can be hard to know the direction. So I’ll put it up to the edge and see how it moves, to confirm that you’re orienting it in the right direction. In which conditions prescribed prism binocularly and monocularly? For ground-in prism I split between the two eyes. For Fresnel prism I only put it in front of one eye because it creates that blur. If there’s a monocular component to the double vision, I always treat the monocular condition first and then we consider prism. If it’s monocular and binocular diplopia, I’ll never be able to create fusion. I think we already addressed the lids. Can we stick Fresnel on the front surface of the glasses? You can, but I find you get more buildup when that happens, so I like to put it on the inner surface of the lens. When do you use induced prism? I don’t do this. It can be done, but I would have to work with an optical. But people do that. What conditions would relate to stable deviations? Thyroid eye disease at some point typically will burn out, so they might be left with a deviation after that. So that’s going to be stable. In patients who have for instance — our patient with a cranial nerve VI palsy, who had a meningioma, after they get treated, if he was not interested in surgery, potentially after a couple of months we could do ground-in prism. I do that pretty often. All my neurodegenerative patients I do ground-in prism, and sometimes it can change. But usually it’s not changing that frequently. That we have to change the glasses every couple months. It’s usually maybe six months to a year, usually closer to a year that we have to make the changes. I’m gonna do two more minutes of questions and then I’m gonna have to sign off here. How do we calculate the oblique orientation of the prism? There are websites that can help you do that. I don’t know them off the top of my head. There are also ways you can honestly draw a triangle and use your hypotenuse to know the correct orientation. Personally I cut the prism just a little bit smaller and I rotate it with the patient in the room. I find that it’s a little bit more accurate. In case of base-out prism, would you perform prism adaptation tests, progressive prism adaptation test before finalizing the amount? I personally don’t do that. I don’t have a lot of experience with that. I usually just trial frame it in the room, either with the Fresnel, or in the trial lens kit, and I actually have them just walk around the clinic, to make sure that they’re comfortable. You can use Fresnel for torsion. Again, correcting the horizontal and the vertical together, although it does have to be rotated, which can be challenging. Would you recommend using a Fresnel prism trial set in the event you don’t have prism sheets available to us? Yeah, if that’s available to you, I think that’s a good option. If your patient gets the Fresnel ordered, I would cut it yourself. Because every patient I’ve ever tried to give it to, to cut themselves, I think all but one have been unsuccessful. You can use Fresnel horizontal in one eye and vertical on the other. But it typically creates so much blur patients don’t like it. I had one patient who requested it. They didn’t like me turning it. But I showed them Fresnel in both eyes and they loved it. It’s very few and far between. Typically can only work if you’re doing a very small amount in the one eye. I think his vertical was a 2 prism diopter, so it didn’t create too much blur. But if you hold up a Fresnel, it creates a lot of distortion, so it’s not ideal. I’m gonna do one last question here. On what grounds would the prism be split between both eyes? Even if the deviation is binocular, you have a right esotropia, I still split it. The reason for splitting it is to make the glasses appear symmetric. That’s the only reason for splitting it. You could put all the prism in front of one eye, but it’s gonna make you see the prism. For an esotropia, you’re gonna have a high amount of base-out prism that cosmetically will be noticeable and probably will be more uncomfortable for the patient. I split it for a cosmetic standpoint, a comfort standpoint, and even if the deviations are in front of one eye, splitting is really just to make the glasses appear better, get less aberration, and just be more comfortable in general. Okay. I’m unfortunately gonna have to stop here. I know we’ve got a lot of questions. I’m happy to share my email if that’s a possibility, if anybody has any questions that I did not — I just saw here how do you prescribe prisms in hemianopic patients? I don’t do that. I refer to low vision rehab team to do that, because they need to work with a rehab and orientation and mobility specialist, for that to go hand in hand. That is all the questions I’m gonna be able to answer today. But I’m happy to share my email if you guys have any other questions about prescribing prism, or potentially we could do another lecture with more in-person video demonstrations. All right. Have a great rest of your day.

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May 6, 2020

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