Lecture: Binocular Vision Part II: Near Binocular Vision Disorders and Interpreting Binocular Vision Results

This live webinar is the second in a three part series and covers common near binocular vision disorders and how to identify these disorders using typical binocular vision testing. In addition to supplying resources to quickly identify disorders, patient cases are discussed to give examples of common history and clinical findings.

Lecturer: Hilary Gaiser, OD, MSc, New England College of Optometry, Boston, USA


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DR GAISER: Hello! Welcome, everyone. I’m Dr. Hilary Gaiser. I’m an assistant professor of optometry at the New England College of Optometry, and today I’m presenting part two of my lecture on introduction to binocular vision testing. In the first part of my lecture, I covered introductory binocular testing procedures, and today we’re going to talk about common binocular vision disorders and the signs and symptoms that you would find with these. Again, I would just like to thank the Orbis team for allowing me the opportunity to present these lectures, and for the help of Dr. Sarah Wassnig and Dr. Catherine Johnson for their part in making these lectures. So today’s lecture objectives is to identify the compensating vergence for all types of phorias and predict if the patient is likely to be symptomatic based on Sheard’s. We touched on Sheard’s in my previous lecture. I would like you to predict the effect of a prescription on ocular alignment using the AC/A ratio. And how to calculate the amps when the amps are measured through something other than the best distance refraction. And then we’re gonna go through Duane White and accommodative diagnoses. We’re gonna provide cases, and we’re gonna classify into the different categories and we’re also going to look at the different accommodative diagnoses and predict the findings. So hopefully at the end of today you’ll have a better understanding of binocular vision disorders. So some review, for those of you who might have not seen my first lecture. I’m just going to go through a quick review of phorias and vergence. So everyone has a phoria that has the potential to become symptomatic, or potentially develop into a tropia. We call this a decompensated phoria. And what prevents that phoria from becoming symptomatic or decompensating? That really is our balance between our fusional supply and demand. Our fusional demand is the phoria at a given working distance. That’s our eye’s natural position. And what do we have to compensate. That’s known as our fusional supply. Our fusional vergence ability. And just note that our accommodation can also add to that supply. So for positive fusional vergence, compensates for exophoria, where eyes are out. We need to bring them in. And we test this with base out prism, like I explained in my previous lecture. Negative fusional vergence is the opposite. It compensates for our eyes being in, and we need negative fusional vergence to compensate, and we test that with base in prism. Just to know that even if you’re ortho, you still need some supply of fusional vergence in order to function comfortably. And it’s just always important that we’re comparing phorias and vergences that are measured at the same working distance. We don’t want to compare distance phoria to near phoria for the same prescription. If we want to test a new prescription, that’s great. We just need to do the testing perhaps with the habitual and then retest with our new prescription. And then just consider the norms and guidelines. So this is just the review of the normative data. This is adapted from Scheiman and Wick. It’s a useful chart to have in clinic. So to review Sheard’s criterion, what is Sheard’s criterion? This is a guideline that states that our compensating fusional vergence should be at least twice the phoria for comfortable single vision. We use our blur finding. We can use break if there’s no blur. And we’re gonna compare our vergence findings to the phoria. So, for example, if the base out to blur is twice the exophoria and eyes are out, we need positive fusional vergence to bring them in. We’re gonna predict comfortable single vision. And the opposite is true for eso. We’re gonna need at least twice that base in to blur of that phoria to predict comfortable single vision. So here is just an example. So we did our cover testing without correction. We found a 2 prism diopter exophoria at distance, and a 9 prism diopter exophoria at near. Our step vergences without correction were base in, no blur, 20/18, and for base out, we found 24, 30, and 26. So is the phoria within the normal range? No, it’s not. What’s our compensating fusional vergence for exophoria? That’s base out. But is Sheard’s criterion met? Yes. So we need at least 18 compensating base out. Which we do. We have 24. So even though the patient has a phoria that’s outside the normal range, they’re likely not going to be symptomatic, because they have an adequate supply of positive fusional vergence to compensate for their exophoria. Just going to go through a second example here. Cover test. We found similar findings. Exact same findings as in the previous example. 2 prism diopter exo at distance, and 9 prism diopter exo at near. Our step vergences are as follows: We found no blur, 20 break, 18 recovery. And for base out, we had 11 blur, 13 break, 7 recovery. So in this phoria, Sheard’s criterion is not met. We have 9. We need 18 to function comfortably. We have 11 for our base out, so our patient is likely to be symptomatic. So you can see in these two cases how we’re looking at what the demand is, what the phoria position is, and what we have to compensate. And in the previous example, the patient would be able to function most likely comfortably. In the second example, they’re not, and we would have to treat them appropriately. A review again of AC/A ratio. We’re gonna look at both the phoria’s compensating vergences and AC/A ratios today when we’re doing the cases, so I just want to give you a quick refresher if you were unable to view my previous lecture. So AC/A is accommodative convergence to accommodation. We determine the change in accommodation when the patient increases or decreases their accommodation by a given amount. We’re using plus and minus one flippers and assessing the phoria, how the phoria position changes, and that’s looking at just how strong the link is between accommodation and vergence. Here is an AC/A ratio example for our refraction. We found -2 in both the right eye and the left eye. So we then did our cover testing through that -2, and found a 4 prism diopter exo phoria. We repeated with +1 in this case, and found a 6 exo. That plus is going to make that exo a little bit larger. We’re going to calculate the difference. The difference between 4 and 8 is 4. So our AC/A ratio is 4 to 1. So our convergence decreased by 4 prism diopters, when the stimulus to accommodation was decreased by 1. So we have our AC/A ratio. What’s the normative data for AC/A ratio? Just to refresh, normal is about 4 to 1 to 6 to 1. Low is under 4 to 1, and high is over 6 to 1. So what’s the clinical application of this AC/A ratio? So, first of all, it helps us classify our binocular vision anomalies. So we need to look at that, either high or low. What does that mean? We can also use the AC/A value to predict the effect of a prescription on a patient’s alignment. And this helps us decide what to prescribe. Do they have a high AC/A ratio? What kind of prescription do they have? Do they have minus or plus? And how is that gonna change their phoria position, if we would need to change that prescription by a small or large amount? So when asymptomatics present with a normal phoria, and you’re finding a large change in prescription, and their AC/A is high, it’s highly recommended to recheck that phoria with the new prescription, to make sure you’re not going to make the patient symptomatic. You don’t want to take a normally functioning patient, give them a new pair of glasses, and then have them back in your office unhappy, because they’re uncomfortable. This is particularly important in the case of esophorias when prescribing minus. Minus is gonna stimulate the convergence system, and it’s gonna make their eyes go in. It’s gonna make that eso worse. Opposite for exophores. When the patient is exophoric and you’re prescribing plus, that’s gonna relax convergence and make their exo potentially worse if they have a high AC/A ratio. So these are the cases we need to be careful. Esos with minus, exos with plus. However, if the situation is in reverse, we can often take advantage of that high AC/A ratio depending on the prescription to help us. So say your patient’s exo. They’re myopic. We might leave them a little overminused, because that’s gonna help to stimulate their accommodative and convergent system and help bring their eyes in. So I have a couple examples here about AC/A ratio and prescribing. So example one: On cover test, uncorrected, we found a 6 prism diopter esophoria at near. They have a quite high AC/A ratio we found of 8 to 1. So what would we predict? So if we predict that we put a +1 over their eyes, and remeasured that phoria, we’re gonna expect a 2 prism diopter exophoria. That plus is gonna relax accommodation convergence, make that exo worse, and so they’re going from 6 to 2. That’s our 8. And we’re gonna expect them to land up about 2 exo. How about if we tested through a +2 flipper? We would expect the exo to get worse by 8 again. So now they’re about at 10 exo. So just be mindful this is a high AC/A ratio. So be mindful that plus can potentially be a little helpful. But minus would make that eso worse. So depending on their prescription, you just need to be aware of this. How about our example number 2? This patient also is 6 prism diopter eso at near. They have slightly low AC/A ratio, almost normal, 3 to 1. So what would we predict? We would predict that phoria through that +1, it’s gonna make the eso a little bit bigger. Yeah. And make the exo a little bit — we’re gonna relax the accommodation a little bit. We’re gonna end up around 3 eso. And then if we do this with +2, they’re gonna end up around ortho. So we can see that a little bit of plus might help the patient, but minus again would make the patient more eso. Previous examples to think about — we might want to trial frame the prescription with the preceding patient, because they have a high AC/A ratio. Might not need to do it with this patient. So I’m just going to review amplitude of accommodation. I covered this in my preceding lecture. I also talk about it today, so I just want to quickly go through that with you again today. The purpose of measuring amplitude of accommodation is to change the focus and response to a near stimulus. It’s tested under binocular conditions. It’s just important to remember to record the first sustained blur. We’re gonna use an accommodative target that’s one to two lines better than best corrected visual acuity. And we do this through habitual correction. This is something we need to think about again, if we’re giving glasses, is how that’s potentially changing, if we’re upping or lowering the prescription by a significant amount. And this also helps you make decisions about accommodative prescriptions. So the Amp stays the same as long as the refractive error is equally corrected. We measure in centimeters but record in diopters. The Rx through which the Amp is measured affects the Amp measurement. This is why you want an up to date prescription before we do the binocular vision testing. For example, if we undercorrected their myopia, this can potentially overestimate amplitude of accommodation. If we overcorrect myopia, that’s gonna underestimate the amps. So if we rule out all of these, we make sure that their add is appropriate, and they’re still having a low amp, we can think about a potential accommodative disorder. Here is just walking through the math in a couple examples. Habitual prescription is a -2. We measure the amps today through this prescription, and we’re finding 5 diopters. However, in today’s distance refraction, we’re finding a change of about a diopter. So now we’re finding a -3. So how is that gonna change the amps? So if we’re starting with a -2, today we’re finding a -3. Essentially that patient in the older glasses has almost a +1 add, if you want to think about it that way. So we want to take that away. So we take away that 1, and now the amps through the up to date prescription is 4 diopters. So that might not necessarily be enough for doing the near work that we need to do, so we need to think about that when prescribing. Let’s go on to example two. Habitual prescription is a +1. Today’s amps through that +1 are 6, but in reality, their up to date prescription is +3. So they’re an undercorrected hyperope by almost 2 diopters. So what is that going to do to our amps? If we correct them fully, they’re gaining +2. So if we were to retest the amps, we would expect 8 diopters. So just thinking about this when you’re prescribing… You might need to prescribe an add, if all of a sudden they have more minus. And so just thinking about amps and how that changes your prescriptions, potentially. So I’m just going to go into the classification systems of functional binocular vision anomalies. So what is a binocular vision anomaly? For review, it’s any non-strabismus binocular vision anomaly or accommodative anomaly. Very common. By definition, they are non-pathological, non-sight threatening, but they can have a significant impact on a patient’s quality of life. Then it’s highly recommended to do a full dilated exam to rule out any ocular pathology, and we always must start out with an updated spectacle prescription. As you saw in some of my previous examples, it might look like a patient has an accommodative anomaly. Then we put on the full spectacle prescription, and things may change. So the disorders that I’m going to be going through today — I only have an hour with you. I would love to go through even more, but this is what we’re going to go through today. Some of the more common disorders. I’m gonna touch on convergence insufficiency, or CI. Also something called pseudo-CI. Convergence excess or CE, divergence insufficiency, or DI, divergence excess, DE, basic exophoria, basic esophoria, accommodative insufficiency, commonly abbreviated as AI, accommodative excess, AE, and accommodative infacility. So I’m gonna present to you today the Duane-White classification system. This is a quite simple classification system that uses patients’ phoria and AC/A ratio to classify patients into different accommodative anomalies. But there’s pros and cons with this and any system. So it’s a very common approach. Again, allows you to classify binocular anomalies based on phoria and AC/A. And then confirm the diagnosis. We’re gonna look at the compensating vergences, accommodation, interaction between the vergence and accommodation system. I’m also going to be — in addition to using these Duane White classifications, going to be discussing some accommodative anomalies. So the cons with this system is it doesn’t address vertical anomalies. It’s really quite simplistic. There’s often overlapping conditions, binocular vision disorders do not always fall cleanly into these categories. There are other systems. But it’s a very easy introductory approach to binocular vision anomalies. So we’re going to be breaking problems down into either convergence or divergence problems. So kind of focusing more on near problems and distance problems. And any excesses or insufficiencies. So if a patient is coming in with complaints that sound more like near, we might focus more on convergence problems, or looking more at convergence problems, and the opposite is true if they’re coming in with what sounds like a potential divergence problem. We’re gonna focus more on distance testing. Duane-White classifies high AC/As as an excess, and low AC/As as an insufficiency. So here’s just a great basic flowchart, when we’re thinking about the patient’s presentation, the signs, and how to classify these binocular vision anomalies. The first we’re gonna look at: Is the phoria greater at distance or at near? If the answer is the phoria is greater at near, than at distance, and we’re talking about the near phoria and the distance phoria being different by at least 5 prism diopters, so if it’s distance — if the phoria is greater at near than distance, and that phoria is an eso, and they have a high AC/A ratio, we’re gonna classify them as a potential convergence excess. Looking again — phoria is greater at near than distance. If the phoria is greater near than distance, we’re thinking there’s a convergence problem in this case. We’re finding exo, and the patient has a low AC/A, we’re thinking the patient might have a convergence insufficiency. So we’re gonna go on to our divergent problems next here. In these conditions, the distance phoria is now the problem. So the distance is greater than near. Again, our distance phoria is different than our near by at least 5 prism diopters. If we’re finding an eso at distance and a low AC/A ratio, we’re thinking there might be a divergence insufficiency. On the flip side, if the phoria at distance is greater than near, and we’re finding exo, with a high AC/A ratio, we’re thinking potentially there’s a divergence excess. So when we’re looking here at our third category, distance equals near, this is more of our basic exophoria, basic esophoria. And this means our phoria at distance is very similar to our phoria at near, by within 5 prism diopters. So these are when it’s greater than 5 prism diopters, distance and near. And this is when they’re about equal. So about — let’s, for example, say ortho in 3, the patient might be — we’re gonna classify them either into a basic eso or a basic exo. So in all of the Duane-White anomalies, we’re gonna find… So we’re classifying, we’re thinking about this. So now we’re going in and measuring our compensating vergences, to examine the problem in more depth. So in these anomalies, we’re going to be finding that our compensating vergences are low in both excesses and insufficiencies. So exophorias are associated with low positive fusional vergences. The eyes are out and we’re having trouble bringing them in. In eso, the eyes are in, low negative fusional vergence, and we’re having trouble bringing the eyes out. If we’re having phorias and if we think back to when I was talking about Sheard’s, high compensating vergences are not a problem. So we’re gonna find compensating vergences that are typically lower in both cases. Both for excesses and insufficiencies. So I’m gonna touch base on the tests I’ve taught in my previous lecture. So we’ve learned some tests of negative fusional vergences, and I taught you base in step prisms for both distance and near. For test of positive fusional vergence, I covered near point of convergence and base out step prisms. I’m gonna add one more test today, that’s just gonna help us when we’re thinking about these disorders. That test is called binocular and monocular accommodative facility testing with flippers. You may or may not be familiar with this. This just kind of helps us when we’re thinking about cases and analyzing things. So the testing procedure: We typically have plus and minus 2 flippers. And we’re gonna be testing the patient at 40 centimeters. The target is 1 to 2 lines larger than the best corrected near visual acuity. And essentially you’re gonna count the cycles per minute of flips between the plus and minus 2 portion. The cycle counts as clearing both the plus and minus sign. So you’re gonna instruct the patient to read the line of letters and report when they’re clear. You’re gonna have them cover. It’s clear. Gonna have them cover. It’s clear. And you’re gonna count the cycles per minute. You can do a full minute. I recommend doing probably 30 seconds, and just doubling it. So the normative data I typically use is 8 cycles per minute, plus or minus 2. There is some research that breaks things down into different age groups that you can look at, finding slightly different things in the 8 to 12 and the 18 to 35 age group. So I highly encourage you to take a look at those studies, if you’re interested. So in addition to counting the cycles per minute for the BAF and MAF, also note if one side or the other is slower. So maybe a patient can get to those 8 cycles per minute, but they’re consistently always having trouble on the plus side. That might potentially indicate a problem. Might indicate that they have trouble relaxing their accommodation. And so what does this help us do? So we do the test binocularly, and then we have the patient close their eyes and then we do it monocularly as well. This helps us decide if there’s a vergence problem or an accommodative problem, or potentially both. So if the patient has a low facility or fails flippers on both the binocular and monocular test, there’s likely an accommodative problem. On the other hand, if there’s low facility only on binocular but not monocular, there’s a potential vergence problem. So if we’re doing it binocularly, they’re unable to do it, it’s vergence — because when we repeat that monocularly, they’re able to accommodate and compensate for the changes in the lens. So we know it’s likely not an accommodative issue if they’re fine monocularly. So this just helps us pinpoint accommodative or vergence issue. So I’m gonna touch base on each of the different conditions. First I’m gonna cover convergence insufficiency. Commonly abbreviated as CI. One of the most common conditions when we’re thinking about binocular vision anomalies. Symptoms in this disorder: Frequent near point complaints, soreness, eye tiredness, asthenopia at near, intermittent blur or diplopia. Often a parent will say: My kid appears to be a slow reader. They might report that words move on a page. They might have frontal headache symptoms, and symptoms are worse at the end of the day. So these might be symptoms that your patient is coming in with, and you might be thinking there’s a possible convergence insufficiency. So when we’re looking at the signs, we’re finding exophoria that’s greater at near than distance at a low AC/A ratio. Again, it’s an insufficiency, so we typically find a low AC/A ratio. They might break down into intermittent exotropia, particularly at the end of the day. One of the hallmark findings of CI is a receded near point of convergence, particularly one that’s more receded when using the red lens over the right eye, repeating the near point of convergence procedure, and more receded with repetition. They do poorly on tests of positive fusional vergence at near. Low base out at near, and they’re going to most likely fail binocular accommodative facility, and have trouble on the plus side of the flippers. The convergence insufficiency often presents with an additional accommodative insufficiency or an accommodative excess. So you might find these together. Convergence excess — same symptoms as convergence insufficiency. So we’re going to have to rely on our testing to differentiate the two. The signs in convergence excess are an eso that’s greater at near than at distance, but with a high AC/A ratio. It’s an excess, so according to Duane-White, we’re gonna find a high or a large AC/A ratio. These patients are converging a little bit more than normal. So they’re typically gonna have a normal near point of convergence. And they’re gonna do poorly on tests of negative fusional vergence. So we’re gonna find low base in prism. They’re gonna fail binocular accommodative facility, and these patients have trouble with minus flippers, and we often find them presenting with an additional accommodative excess. In divergence insufficiency, we’re having distance complaints. Intermittent blur at distance. Eye tiredness, eye strain, asthenopia at distance. Particularly patients often complain of having trouble during night driving. Motion sickness, things like this. And we’re looking at our signs, we’re finding esophoria that’s greater at distance than at near. And they have a low AC/A ratio. Again, it’s an insufficiency of AC/A ratios. Typically low. Typically they have a near normal point of convergence, and they do poorly on tests of negative fusional vergence at distance. So low base in. In divergence excess, patients frequently may not have complaints. They might have occasional diplopia, but that’s rare, because the eye tends to suppress. They might have photophobia, and cosmesis is often a concern. They might say friends and family say I look bug eyed, my eyes are out, and that might be one of the symptoms or complaints. Looking at the signs, the exophoria is greater at distance than at near, so you’re expecting the phoria to be worse at distance than at near. And it’s an excess, so they’re going to have a high AC/A ratio. They might often have a large exotropia when looking far away, and there often can be associated with it a V pattern tropia or exophoria pattern. I’m gonna go into that in a little bit more depth later. And they have a normal near point of convergence. These patients do poorly on tests of positive fusional vergence at distance, and we’re going to find low base out. So this is what I mean when you might see a V pattern exo. You might be looking at the eyes, and they look accurate, but then when they go up, all of a sudden they go out. So when you’re looking superiorly, the eyes look like they go out into a V. And this is known as a V pattern exo. So next you’re gonna look at your basic exophoria. We have a combination of symptoms that are similar to convergence insufficiency or divergence excess. You can think of these as exo symptoms. Their eyes are out. They’re having trouble coming in. Things like that. Our clinical signs are an exophoria that is equal at distance and near. Again, within that 5 prism diopters. So we’re finding very similar exo distance, near. Typically also find a receded near point of convergence, and these patients do poorly on tests of positive fusional vergence, both at distance and at near. So you’re gonna find low base out vergences, distance and near. Typically fails binocular accommodative facility. And they’re gonna have trouble with plus flippers. Basic esophore… Again, gonna have those eso symptoms. Their eyes are in. They’re gonna have a combination of symptoms that sound like CE, convergence excess, or divergence insufficiency symptoms. Clinical signs again: The esophore is gonna be similar at distance and at near, again, within that 5 prism diopter amount. These esophoric patient have a normal near point of convergence — eyes are in, trouble moving eyes out — so we’re gonna find low base in vergences, distance and near. They’re gonna fail binocular accommodative facility, and they’re gonna have trouble with minus flippers. They’re already accommodating, already converging. Can’t really do more when we put the minus flippers on. So I’m going to go into our accommodative conditions next. Frequent complaints are blur, eye strain at near. We’re looking at our sign for finding low amplitudes of accommodation. And they’re gonna fail lenses on both binocular and monocular accommodative facility. Right? This is an accommodative issue, so they’re gonna fail it when we have both eyes open binocularly and monocularly. They’re gonna have difficulty with minus on the flippers. Can’t stimulate their accommodation. Can’t use that. And they’re typically a little esophoric at near. So this is a great time to touch base on something called pseudo-CI, or pseudo-convergence insufficiency. So your patient is coming in, they’re having complaints. It sounds like a convergence insufficiency. So you go to evaluate that. You’re finding an exo that’s greater at near than distance, and then your point of convergence is receded. You’re thinking: Oh my patient has convergence insufficiency. But then you note that symptoms appear to improve with plus lenses. And this doesn’t make sense. Right? So what’s going on? So what’s happening is: Those low plus lenses are giving the accommodative system kind of a kick start, if you want to think about it that way. That’s gonna help activate our accommodation. Once the accommodative convergence system is stimulated, we’re gonna reduce our exo. That’s gonna reduce our demand on fusional vergence. So the root of the problem is accommodative insufficiency, and we’re using plus lenses to help out that accommodative facility. And then if we retest, things look normal. So it’s really important, whenever you suspect convergence insufficiency, based on your cover test and point of convergence, just be sure to always quickly test the +1, to rule out accommodative insufficiency or what I’m calling pseudo-CI. So we covered accommodative insufficiency. I’m going to cover accommodative excess. So symptoms — distance blur, particularly after near work. Headaches associated with near work. Eye strain. And for our clinical signs, we frequently find very variable visual acuity and ret and refraction that don’t make sense. Sometimes some practitioners refer to this as pseudo-myopia. Maybe you’re having 20/30 visual acuity, but we’re not really finding anything on ret and refraction and vice versa. Things just aren’t making sense. Typically find high amps. Patients are gonna fail binocular accommodative facility and monocular accommodative facility flippers. So they’re gonna fail monocular and binocular. Whereas the vergence issues would likely pass the monocular but not the binocular. And these patients are gonna have trouble clearing plus on the flippers. And typically, they are a little esophoric at near. Maybe also at distance. So now I’m going to go into what’s called accommodative infacility. Symptoms include just difficulty switching focus from distance and near, back and forth, difficulty with reading. Maybe some intermittent blur associated with near tasks. The sign that a patient fails both binocular and monocular accommodative facility, and you know that the patient cannot do either side of the flippers. They’re having trouble with both the plus and minus lenses. Their accommodation in either direction is ill-sustained, not able to clear the flippers. So now I’m gonna go into some patient cases, and we’re going to look and diagnose the patients. I do recommend maybe you want to have a piece of pen and paper for these, if you want to jot down any notes. I’m gonna ask you to diagnose the patients after I present the cases. So for the cases I’m gonna present a history, entrance testing, refraction. Maybe additional BV testing. You’re gonna help me diagnose the patients, and then we’re gonna go through each of these cases. So in case number one, we have a 25-year-old female that’s presenting for an eye exam. She has the chief complaint of blur and eye strain. We’re finding that the blur is intermittent, and typically starts maybe an hour or so after computer work. She reports that it is in both eyes and it’s constant. She recently switched to a desk job, and she’s having a really hard time with her blurry vision. She’s also reporting occasional double vision when tired. And she finds relief after taking a break. She’s not currently wearing any glasses. She’s worried about her job performance at the new job, and she’s just having trouble doing it. So on entrance testing, this is what we’re finding. Her distance visual acuity, uncorrected, is 20/20 in both the right and the left eyes. Same for near. On cover tests, we’re finding ortho at distance and a relatively high exo, 10 prism diopters, at near. Motilities are fine. Push-up amps are 10 in both the right and the left eyes, and her near point of convergence looks a little receded. It’s 15 and 25. Stereo vision is normal, pupils are normal. So when we go to do refraction, we’re finding plano. Not finding any refractive error. We’re not finding anything on refraction. So then we’re gonna go do some additional binocular vision testing. So again, without correction, the patient was ortho at distance. 10 exo at near. So we’re gonna repeat that cover test without correction. Obviously the patient is plano. +1, to see what her phoria is and assess her AC/A ratio. In this case, we’re finding 12 prism diopters of exophoria, which gives us an AC/A ratio of 2 to 1. That’s low. Our step vergences are as follows: At near, base out, 6/18/4. Base in, 8/10/7. Looks a little low. So is Sheard’s criterion met in this case? This is something we should probably ask ourselves. So the patient is 10 exo. The compensating positive fusional vergence for an exophoria — in this case, the blur was 6. We need at least 20 for the patient to be able to comfortably compensate for that exo, so she will likely be symptomatic. We note that the patient has difficulty on the plus side of the flippers, on both binocular accommodative facility and monocular accommodative facility, and she fails the binocular accommodative facility, but she’s fine with the monocular portion of that test. So I’m going to ask you to diagnose the patient. What do you think this patient has? I’m gonna put up my previous slide, so you can see the patient information. And what is your diagnosis? Okay, so we had quite a few answers. The majority said convergence insufficiency. That would be a good diagnosis. So we diagnose this patient with convergence insufficiency. And why was that? The patient had a large exo, receded near point of convergence, they had a low AC/A, so you’re thinking insufficiency. They did poorly on tests of positive fusional vergence, and they failed the plus side. They were having difficulties with the plus flippers. Amps were normal, so we were ruling out accommodative issues. And the patient’s findings don’t improve with plus. So we can rule out pseudo-CI or any accommodative insufficiency. Great job. So let’s go to case number two. In this case, we have a 16-year-old female who’s coming in for our comprehensive eye exam, with a complaint of tired eyes while reading. The patient reports the symptoms occur almost every single day, and has been going on since the beginning of the school year. She tends to reread sentences. She does wear glasses full-time, and her symptoms improve after taking breaks. She’s really worried about her school performance. So we do lensometry on the glasses to find it’s -2.25 in the right and the left eye. Here is our entrance testing. So with her glasses, she’s 20/20 at distance and near. We’re finding she’s ortho at distance, and she has a large exophoria at near with her glasses. Amps are 13 in both eyes, motilities are good. We repeat testing with the red lens and find she’s even more receded. Pupils are good, and stereo seems to be a little bit reduced. Again, we do an up to date refraction. Same as her habitual today. So we move on and do some additional testing. On this additional testing, we’re finding that she’s ortho at distance and near, just like when she came in. We’re gonna repeat the cover tests with the +1 flippers, when we find that she’s now a 5 exo. So we go to calculate that AC/A, we’re like… Is that 5 to 1? That doesn’t make sense. We’re using +1. We expect that exo to get worse, but it’s not. It’s getting better. So the exo gets better with the plus flippers over the habitual. And we repeat the near point of convergence with the +1, and we’re finding that the near point of convergence is now 5 and 6. And that improved from 14 to 16. So that also doesn’t make sense. So we’re thinking… We’re asking ourselves… What’s going on? So what do you think is going on? What is your diagnosis for this patient? And again, I’m gonna put up the information, if you need it. So what do we have? Large majority are saying pseudo-insufficiency. So let’s look. In this case, we’re gonna diagnose the patient with accommodative insufficiency, or pseudo-CI. So we’re just noting the effect of the plus. We’re initially suspecting CI. They had a large exo at near. We see it at NPC, retest with plus, and then we’re finding that things are improving. So that’s not a CI. A CI would do poorly at plus on near. So we’re thinking there’s an accommodative insufficiency. We’re gonna think about maybe prescribing some plus or a bifocal here. Let’s move on to case number three. It’s an 11-year-old female. She’s presenting for her first comprehensive eye exam. She was referred after a school screening, due to decreased visual acuity. She tends to squint. The patient reports that it’s daily. Kind of started at the end of the last school year. It’s in both eyes and all day. She’s not really finding relief when she’s taking breaks, and the patient’s mother reports that she’s struggling in school. So we go on to do our entrance testing. We’re finding reduced visual acuity at distance, uncorrected. Fine at near. Uncover test — again, she doesn’t have glasses yet. Finding 3 prism diopter exo at distance and 14 prism diopter exo at near. So phoria that’s worse at near than at distance. Finding the amps to be 17 in both the left and the right eye. Motilities are fine. NPC with the light target is receded. Pupils are fine. Stereo might be a little reduced, but not too bad. On refraction, we’re finding a 1.25 refractive error. Both right and left eyes. So we’re finding a refractive error. We’re finding a relatively significant — the patient wasn’t wearing glasses. Now she’s a -1.25. So let’s retest. Let’s find out what’s gonna happen. Maybe this is gonna help her symptoms. So we repeat our cover test findings through the trial frame, and now we’re finding a 4 exo. Just to go back to when she came in, she had a 14 prism diopter when she came in. Prerequisite we’re gonna repeat the near point of convergence. We’re finding that it’s improved. Again, she’s now 2 to break, 4 for recovery. So both the exo and NPC improved. We did a trial frame, went from plano, no prescription, to -1.25. So we can get an estimate of her AC/A ratio. We’re gonna calculate that at about 8 to 1. She went to 14, now she’s 4, we’re doing this with a 1.25. So that’s a relatively high AC/A ratio. So because she’s minus, because she’s myopic, we can take advantage of that high AC/A ratio to help with her large exophoria. So what is your diagnosis for this patient? What does she have? Great. The vast majority say there was an incorrect glasses prescription, followed by divergence excess. So patient is diagnosed with a large exophoria, secondary to uncorrected myopia. And with that correction, they were now within normal limits. So this is why I keep stressing the importance of having a full, up to date refractive correction, before we diagnose patients with accommodative anomalies. Because we might just find this case. So uncorrected myopia is associated with exophoria. We’re gonna correct significant refractive error before proceeding with testing, and we can take advantage of that high AC/A ratio. So she does have a high AC/A ratio. Might eventually look at that a little bit closer. Do some more binocular vision testing. But today we’re gonna diagnose her with a large exophoria, secondary to that uncorrected myopia. Let’s take a step back. So our initial amps were 17, both right and left eyes. So what would you predict the amps to be, now that she’s fully corrected? So now we’re correcting her with -1.25. So if you want to think about it, she was previously in an add of 1.25, being uncorrected. So we’ve got to take that away. So she was 17. With full correction, we’re gonna take away that 1.25, so now if we remeasured her amps with her new glasses prescription, it would be approximately 16 diopters. So let’s look at case number 4. 23-year-old black male, is an optometry student, coming in for a comprehensive exam, because he’s having eye strain while studying and blurry vision at distance after studying. The patient reports that this happens multiple times per week, and his symptoms have been worse since starting optometry school. He reports the blurry vision is in both eyes, worse at the end of the day. Does report that his symptoms are relieved with breaks. Having trouble studying for his classes and worried about his grades. This is what we’re finding on our entrance testing. Reduced visual acuity at distance in both the right and left eyes, patient is ortho at distance, 5 prism diopters esophoria at near, push-up amp 12 in both eyes, for near point of convergence, we’re finding to the tip of the nose, and stereo is 30 seconds. On retinoscopy, we’re finding a little bit more minus than what we would expect for 20/30 visual acuity by a little bit. But when we do subjective refraction, in this case we chose to do a delayed refraction. A little bit more plus, letting the patient sit there for a while. You can also do cycloplegic refraction. When we want to take accommodation out of the picture. We’re finding the prescription to be plano and a little bit of plus. So we’re finding a reduced visual acuity. The subjective refraction is not matching that entering visual acuity. On ret, we’re finding more minus. So there is this mismatch. It’s not really making sense. The ret and refraction, so we go on to do more binocular vision testing. We’re finding that the patient is ortho at distance. 5 prism diopters eso at near. This is when they were coming in. We’re gonna repeat that cover test through -1, and now we’re finding a 13 prism diopter esophoria. We’re finding that the AC/A ratio is high. It’s 8 to 1. We do our step vergences near base in and base out. Looks maybe a little low on base in. Sheard’s criterion is not met in this case. There’s a 13 prism — sorry, 5 prism diopter eso at near. At least 10 compensating base in, negative fusional vergence. And we have 8. So Sheard’s criterion is not met, so the patient is likely symptomatic, which they are. And they’re unable to clear the plus side of flippers in both binocular and monocular accommodative facility. So we’re thinking there might be more than one system here. So what is your diagnosis in this case? The vast majority said combination of convergence excess with accommodative excess. So that’s what we also diagnosed the patient as. Divergence excess with accommodative excess. Just to remind you that vergence and accommodative anomalies are often linked, often occur together, so we need to analyze both vergence and accommodative tests. We decided they had an esophoria that was greater at near than at distance, and reduced negative fusional vergence. They had signs pointing to accommodative excess. High amps, unable to clear the flippers, and when this happens, you might think that the patient is having an accommodative issue. So let’s go into case number five. Nine-year-old Asian female presents for a comprehensive eye exam. Comprehensive eye exam after being referred for a school screening. She’s having some difficulty seeing small print on the blackboard. She’s reporting blurry vision whenever she’s looking at distance, and she noticed the onset gradually over the past three months. Patient’s mother reports she’s occasionally closing one eye when looking far away, and her daughter appears to be sensitive to bright light, since she frequently closes one eye at distance, but is doing very well in school. So on entrance testing, what are we finding? We’re finding reduced visual acuity at distance, 20/60 in both the left and the right eyes. On our cover test, we’re finding 16 prism diopters of exo at distance, and 7 diopters at near in primary gaze. When we do our motility, we’re noting a V pattern exo. NPC is a little receded. Pupils are fine. And we’re finding this when we’re doing our motilities. Refraction is a little on the myopic side. So we put those subjective findings into our trial frame, and we’re going to repeat the cover test. When we do so, we find that the cover test findings are now better. We’re finding 7 prism diopters exo at distance and ortho at near, and now her near point of convergence is to the tip of the nose. So what is your diagnosis for this patient? And I gave it away a little bit. Divergence excess. So we did diagnose this patient as a divergence excess. We found myopia, so we corrected that refractive error before proceeding. This fixed the near point signs, but the patient still had distance symptoms, so we prescribed and we’re set to follow up and monitor her symptoms. So on our follow-up, we have the patient return. She had no near point symptoms, no eye strain or diplopia, but she still has a little bit of those divergence excess findings. Not so bothersome with the correction, so we’re helping her out, being fully corrected, but she’s still a little bit divergence excess. Okay. I’m gonna go into our last case. This is an 18-year-old patient. Just started college, and having blurry vision while reading. Patient reports his symptoms started immediately after reading. He reports trouble with both eyes and that his symptoms are relieved after breaks, and he has been avoiding reading, and he’s worried about his grades. This is what we’re finding on entrance testing. 20/20 visual acuity, distance at near, cover test is finding ortho at distance and at near. Push-up amps are low. Motility is fine. Convergence is to the tip of the nose and stereo is reduced. This is what we’re finding for subjective refraction. And so we do some additional testing. So we retest with +1, want to know our AC/A ratio, we’re finding eye AC/A ratio, borderline high is 6 to 1, and we’re testing our step vergences. So we’re gonna ask ourself: Is the compensating vergence through the +1 adequate to compensate for the phoria? And it is. So we’re finding that he’s able to compensate for that 6 prism diopter, so we might want to think about: Is that +1 helpful? So I’m not gonna ask you this one, but what is the diagnosis in this case? It’s a diagnosis of accommodative insufficiency, and so we tested with the +1. That’s kind of what we were thinking might help the patient to make up for the lack of accommodation, and it seems to work. So we trial frame that extra plus, and we’re gonna prescribe that for the patient. So just to recap today, you should be able after today’s lecture to identify the compensating vergence for all types of phoria and predict if a patient is likely to be symptomatic. We’re gonna predict the effect of a prescription on ocular alignment using the AC/A ratio, and calculate the amps when the amps are measured through something other than the best distance refraction. We also took a look at Duane-White and accommodative diagnoses, and hopefully when you are doing patient cases, seeing patients… Into different categories. Do you have any questions?

>> Thanks, Dr. Gaiser. So far there are three questions, if you want to pull up the Q and A.

DR GAISER: I’m gonna click on those. Oh, good question. So when a patient with binocular vision anomaly comes to clinic, do we assess the vision first, or binocular vision assessment? If this is your first time seeing them, I would recommend doing a full comprehensive exam. We’re gonna come up with a new prescription, check for eye health issues, and potentially go on to do a binocular vision assessment and have them come back later to do that. So first we need to do an assessment, do a refraction, look at eye health, rule various things out, and then we can do our binocular assessment. Next question is, I believe, about minus lenses. Minus lenses are gonna stimulate accommodation and convergence. So we might potentially overminus the patient. I think that’s what you’re asking. That overminus can help stimulate convergence as well. The answer would be yes. And then I got a question… We’ve got to have a question about: What age should we still look at the AC/A ratio. You can do it in any age. But you just need to compensate and make sure the patient has an up to date add. So if you’re having an adult that’s having issues, you can do it as well. I think that’s it. Unless there’s any more questions.

>> That looks like it for now. Maybe we’ll wait a couple seconds.

DR GAISER: I’m going to adjust my light.

>> If anyone has questions, you can ask those.

DR GAISER: Oh, I’m getting a question on divergence insufficiency. And my preferred prescription. I’m gonna be covering treatment in part three of my lectures, so I’m gonna save that question until that date. For my third part. When I cover how to do basic vision therapy and what to prescribe for the common binocular vision complaints. There’s a question on… Is there any relation between convergence insufficiency and contraceptive pills. To my knowledge, there isn’t. I haven’t seen anything in the literature about that. Getting a question: If a 39-year-old patient has a myopic correction for distance, but also accommodative insufficiency, what are we going to do? We likely might put them into an early bifocal. We’re gonna fully correct them for distance, but they’re having problems up close. Depending on their prescription, maybe they can take off their myopic glasses and have some add that would help them. But I would recommend more bifocal correction, where they have distance and then an additional add for reading. I’ll cover this a little bit more in depth again when I cover the treatment portion of binocular vision anomalies. I’m getting an interesting question on what would be a good book to read on this topic. I like this question. I find Binocular Vision by Scheiman and Wick to be very helpful. You might want to look into that. I’m getting some more questions on treatment. For an emmetrope with accommodative insufficiency, do you prefer to give single vision reading glasses or progressive — again, I will save these treatment questions and cover them in part three. It kind of depends on the age of the patient. The progressive addition lenses are a little bit difficult for thinking about prescribing to children. I might do single or bifocals. Another follow-up question on the minus stimulates convergence. Right. If you’re fully corrected, you’re not overminused, you’re not gonna stimulate convergence. This is just simply in the context where we have a habitual prescription, we might be adding plus or minus flippers on top of it, and that minus is gonna stimulate convergence. Again, this is why I always talk about: The patient must be fully corrected first, and then we’re adding lenses on top of that. We’re doing things on top of that, to see if there’s any issues. And then a question on convergence insufficiency and spasms. Possibly. First you’ve got to evaluate and address the CI, and then maybe do testing and see if there’s any spasm related to that. So I think I’ve answered all the questions. MEM is great. With retinoscope, I just unfortunately didn’t have time to cover that, but MEM, if you know how to do it, that tests your lead in the lag of accommodation. It’s a great technique. I do it quite frequently. Unfortunately, I only have an hour to spend with you. I wasn’t able to talk about that in either my preceding lecture or today. But it’s a great test to do. Next question: Are convergence insufficiency and accommodative insufficiency common for patients undergoing — or after refractive surgeries? If they’re done correctly, they shouldn’t — accommodation issues and convergence issues aren’t gonna change necessarily, as a result of refractive surgery. It’s just simply fully correcting the patient. Which treatment is better for spasm, atropine or plus lenses? I’ll hold these treatment questions, again, like I said, until part 3, and I’ll answer them more fully in depth at that point.

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June 18, 2018

Last Updated: October 31, 2022

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