The objectives of this lecture are:
1. To describe different definitions of Esotropia and Exotropia
2. To present surgical and non-surgical management
3. To discuss reasons for early intervention of esotropia
Surgery location: on-board the Orbis Flying Eye Hospital in Yaoundé, Cameroon
Lecturer: Dr. Carlos Solarte, University of Alberta
(To translate please select your language to the right of this page)
Dr. Solarte: Okay. So welcome, everyone. My name is Carlos Solarte. I’m originally from Colombia, but I live in Edmonton, Canada. I am the lead direct of the ophthalmology director at the University of Alberta. Let’s start with two very common problems esotropia and exotropia.
As you can imagine, you have no conflict of interest of any kind. All the images you are about to see, most of the pictures are from a book which will follow. And the book belongs to Dr. Scott Lambert, Christopher Lyons, and it’s called “Taylor and Hoyt’s Pediatric Ophthalmology and strabismus.” This is where most of the pictures have been obtained for this conference.
My objective today is I want to talk about esotropia and exotropia. I want to talk to you about management, both surgery and no surgery. Very important. Why we want to do with those babies with esotropia. So let’s go. Esotropia is just the inward deviation of the eye by any means.
“Tropia” means” position,” “Eso” means” Inward.” Maybe you would like to call it “Endo.” And in Spanish, we call it endotropia. That is one. So inward deviation can happen by many ways. Let’s take the definitions. We call it congenital when you see it before in the first 6 months of life. Infantile if it’s less than a year, but older than 6 months. And acquired if it goes from 1 year and above. We have two conflicting theories about why this is happening.
So we have two persons, Claud Worth and Chavasse with two different theories. The first one is, “The essential cause of squint is a defect of the fusion faculty.” Therefore, irreparable. Chavasse says something different,” Most infants with congenital squint are capable of developing fusion if the deviation is fully corrected before the age of 2.”
Let me ask you something what is fusion? Do you know what fusion is? Let me ask you this question different. You have two eyes. Why don’t you see double? Fusion. Because your brain makes two images and merges one with the other one, so you only see one. That is called “Fusion.” That’s why you do not see double.
Epidemiology. Esotropia only happens in 0.25% of the population. So it’s not a big number. 0.25. Exotropia, the opposite, happens in 1% of the population. I’m going to give you an example. Japan has 7:1 ratio. So per one esotropia, they have seven exotropias. So normally it’s four times more, and Japan is seven times more. Esotropia, the incidence is decreasing because now we have massive campaigns to diagnose and retreat refractive errors.
The rate of surgery remains unchanged, but we are treating more glasses. We are using more glasses now. And we have some company, we might have the dad or the mom being affected, and the child being affected. This comes described as being co dominant. I don’t want to go into the genetics right now. But it’s
The onset of esotropia happens very soon after birth. Between 2 to 4 months of age. Now, most of these moms will tell you that when they have the babies, they see something different. So moms can feel it. And it comes to you. In normal development, by the age of 4 months, the eyes shall be straight. When the babies are little some esotropia may regress, but if the angle is very large, only 2% will regress.
So the question is, questions we need to start asking. Remember, pediatric ophthalmology is about asking the right question at the right time. So we have to ask the mom, mom, is this all the time, or some parts of the time? So you need to know, is this variable or intermittent? Is the refraction less than 3? Why 3? Why not zero? Because the site of refraction, the refraction at the age of 4 is expected normally to be 3. That’s called physiological hypermetropia.
So we have to examine the baby. Okay. Now you have a baby in front of you. Who of you are moms and dads? Who is not a mom or a dad? Do you get scared of babies? Do you know how to examine a baby? It’s difficult. It’s not easy. So we have to be sure that we use everything we can to answer the questions.
We use different situations. We have Krimsky test. We have Hirschberg test. Bruckner the cover test, which is going to be our gold standard. And we have to say that up to 50% of mistakes are pre op measurements and why we do so many re operations. That is why we do not know I graduated from a center, and one of in Colombia called Barraquer Institute. Jose Barraquer very famous ophthalmologist. Used to tell us every time, you do not know how to diagnose, don’t even try to do this surgery. You need to be sure that you can diagnose if you want to treat it. Hirschberg test is very easy. You are just using a pen light. A pen light or a flash light. And the only thing you’re doing is flashing the light to both of the eyes and you’re looking where their reflex is in the cornea.
You can see in the right eye it is right in the center, but in the left eye, you can see, is not in the center. So you know you have an esotropia of the left eye. How do I know it’s left? Because the person is fixating with the right. That’s why I have the light in the center.
So if this is an exotropia, the light will be in the opposite side. If this is a hypertropia, and the eye is up, the light is going to look in the lower portion. The question is, is there any specific distance? Yeah. You have to consider that the farthest you move into the room, the more the lineation is going to change. So Hirschberg is done in a normal working distance of maybe a meter or two. We can do Krimsky test. It’s exactly the same as Hirschberg. The only thing we do differently with Krimsky is we add a prism. And take a look at how, if you compare A, B, or C, you can see how in number A in A, there is a Hirschberg. No lens. No prism. In the B there is a prism. And in the C, with the use of the prism, now both eyes are straight. Or the light is in the center. Let me say it that way. So this is the measurement that you needed.
So this is how you know how many prism diopters of deviation you have. What are we doing here? Is this a Hirschberg or a Krimsky? A Krimsky. You can see they’re using a lens in a kid that’s really looking to the front and we’re looking at that. Now, there is something also called the Bruckner test. Excellent question. She’s asking, in which eye shall we place the lens? Do it in the fixating best eye, or the deviated eye? What do you think? We use it in the deviated eye. We let the fixating eye to be the fixating eye.
Bruckner Bruckner, it can be a little bit tricky to do because it uses something similar, but uses the red reflex. This picture specifically you can see that the fixating eye has a very nice red reflex and the other one has a different color of the reflex. But that also depends on the quality of the red reflex too. And that goes in skin color as well. That changes the reflex.
In this case, this might be misunderstood as leukocoria, which it is not. Many people prefer to use Bruckners, but I do not. I prefer to use Hirschberg or Krimsky more than Bruckners. So it is difficult this is dilated, here. But you can do it without dilation. It’s difficult because a pupil is small, you might not see the red reflex. The other one, which I don’t have a picture, is the cover test. The cover test is extremely important. It’s the gold standard. And we have to use a target of 20 feet or 6 meters. We just cover one eye at a time.
It’s called the cover test. We cover that eye. Or we do alternating cover tests. Which you do wiggle, wiggle, side to side. That is the most accurate reading for measurements with the prisms. That works excellent in kids which are 3, 4, 5 years old. Try to do it with a 13 and 14 month old kid, good luck. It’s difficult because they don’t want you to be close to them.
So we have to use Krimsky, we have to use Hirschberg, we have to use everything we can. We can do briefly cover this, fantastic. This can be very challenging. Alternate cover. Alternate cover. Yep.
Okay. So we have, now, pseudo esotropia, some people call it pseudo strabismus, which is very common. Seen almost every day. Pediatricians see this every day in their clinics. Now, what is esotropia? Esotropia it be very easily confused with true esotropia. So we have to say it is confirmed with Hirschberg, Bruckner and our cover test that the eyes are straight. But the mom is going to keep looking at you and saying, no, you’re wrong. Because it’s very easy to see with very broad epicanthal folds. See here. Mom has been claiming this is an esotropia here. What do you think? What do you think? Is it an esotropia or not? So is this eye inward or not?
Look at the reflections of the flash. They are exactly in the same position. They are exactly not exactly in the center, but exactly in the psalm position in both eyes. So this is a pseudo strabismus. So let’s go into one very commonly seen. What we call accommodative esotropia. The most common of all.
So what happens is that we have three different scenarios that we have to go here. This is number one scenario is what we call so let’s define, first, what is accommodative esotropia. Let’s define it. It’s an esotropia which is related, 100%, to the refractive error. Meaning meaning the kid has large or esotropia. You put the glasses on, esotropia is gone. That’s what we call “Fully accommodative esotropia.”
But this esotropia is the same in near or distance. Doesn’t change. Glasses on, problem fixed. Normally quite high hypermetropias around blast 4, blast 5. Number two. What we call high AC/A ratio. Brazilians should know what AC/A means. Yes, exactly. My French is limited, but I can understand a little bit. Yes. Right here. Exactly.
This is just a measurement of accommodation. I’m not going to go into the formula, how we calculate it all of that for the nursing and for the personal. This is a measurement accommodation. And in this situation, that is excessive. So it’s too strong. So imagine, in the distance, eyes are straight. Perfectly. Wonderfully. But when they look near, the accommodation goes high and the medial rectus contracts for the accommodation. And in that specific case, that’s when we need bifocals. Bifocal glasses.
So we have the refractive esotropia with high AC/A ratio. We have the same this problem is these two combined. Needs glasses, because this one only needs bifocals, but this person needs glasses plus bifocals. And we can say when we call it “Early onset accommodative esotropia.”
What is the meaning of that? We just imagine the 4 month old baby with dilated pupil. And we find the baby’s plus 7. We get the glasses and the eye is perfectly straight. So this is a fully accommodative, but early onset.
So let me just show you an example. Lovely girl. Lovely girl. What do you see? Do you see an esotropia? Okay. I’m going to tell you the story behind. The refraction is plus 6. We get the glasses on. Big change, huh? From here to here. Just by using glasses. Now, the next question that you as ophthalmologists need to be able to answer is, the mom is going to ask you, how long does my child have to use glasses for? It’s a plus 6. What are you going to answer?
If the power never changes, most likely will have to use glasses for life. If the glasses do not change, oh, sorry if the glasses change and the prescription goes lower, like in this case, this is the same girl at the age of 15. The refraction magically came to plus 1 or plus 2, and now the eyes are straight. No intervention. No surgery. Nothing. Okay?
Partially accommodative esotropia. So despite using full prescription, only a portion of the esotropia is corrected. Small residual angles breaks fusion and produce amblyopia. So what is the meaning of that? So we get the glasses on. The person has an ET of 50. And now, after glasses, it’s an ET of 20. It’s going to fusion going to work? Most likely no. Because the images are too apart.
So this produces amblyopia. The brain is going to choose one image or the other one. Some people may not want to use bifocals. Or adults who have no minimal minimal hypermetropia. So these persons are the persons who need surgery done. You have done glasses, you have done patching, you have done everything. Now it’s time to do something. And now is when surgery, most likely, is going to be needed.
Signs of alarm. Cross fixation. What is this? Why do we call it cross fixation? Why? The right eye is looking at the left side, the left side is looking at the right side. So esotropia is so large that the brain is confused because everything is backwards. This is a sign of awe alarm because this baby needs to be treated as soon as possible. We need to break the cross fixation in order to improve fusion.
We have a special form of esotropia too. Trauma. Can you give me an example? Can you give me an example of trauma? How about how about if I say, medial rectus sorry. Medial orbital wall fracture with entrapment of the medial rectus. So the eye will go will go in. Is that congenital? No. Does the person know how to deal with that? No. It’s acute. So it’s acquired.
What is the first symptom this person is going to have? Double vision. Dramatic double vision. This is an example of reconstructive strabismus. Can you give me another example of reconstructive strabismus? I have another one for you. How about thyroid disease? That’s it. The most common one. You are right. But thyroid disease is one of the ones that we see very often.
Palsy, diabetes, syndromes. Duane syndrome, Moebius syndrome. Or something called “Heavy eye syndrome.” You might not know this. That’s part of my research too. Take a look at the left eye. In the best interest of time, let’s go into the left eye only. Left eye, look the at left eye. It’s inward in all positions of the gaze. So if you go to the mid center position, you can see significant esotropia of the left eye.
You go to the right side, and esotropia, unchanged. You go to the opposite direction, to the opposite place, and you see that the lateral rectus of the left eye is definitely not working. Right here the left eye should be moving to the left, which it’s not. Looking to the left and up and left, you can see that the left eye does not elevate either.
So what happened? I will give you an example. I’m not pretending to teach you anything about this. Talk a look at this. So this is the patient. The CT scan. And at the lower portion, you’ll see the two how this glove is so large and so big that the glove has displaced the superior rectus nasally and the lateral rectus inferiorly. The superior rectus is not in its position. It’s nasal. So it doesn’t work. So this eye does not elevate. And the lateral rectus is lower, so the lateral rectus doesn’t pull out. Is it fixable? Yes.
But we’re not going to talk about this. This is just an example of how esotropia can be due to many, many different reasons. Okay. You have spoken for half an hour already. So I’m planning to go as you see, I didn’t say anything about management yet.
Because the management of ecosystems and esotropia is very similar. So let’s go back into ecosystems first, shortly, and then we’re going to the muscles and what we do. What kind of surgeries do we do for each one of these ones.
Ecosystems, we have so many kinds. So number one in ecosystems is we have what we call “Intermittent ecosystems.” Basic ecosystems. What we call divergence excess type. Convergence insufficiency. Or associated to syndromes. All that’s acquired. So intermittent ecosystems is an imbalance between convergence and divergence. Intermittent ecosystems happens for some time and then the eye becomes perfectly straight again.
It’s a typical example that the mom tells you the cud goes XT, but during the examination you are not able to find it. Because the patient can control it. And that is why it’s difficult to see it sometimes. Because this is an imbalance between convergence and divergence when the patient is tired, hungry, or after a couple of drinks in adults. You see that the eyes are starting to go outward. And that’s why you see it more often. So this is difficult.
Very typical you’ll see like this. Two brothers. It’s not the same person. It’s two brothers. One is outside with the eyes perfectly open, and the other one has one eye closed. Ask your patients if they close one eye in the outdoors or not. Most likely the answer is “Yes.”
Basic ecosystems. That one that is permanent. It’s all the time the same. Never changes. We always measure in the distance. We always measure near. So it’s unchanged. It’s the same for distance and near. It’s very stable over time. And the onset can happen at any time in life, but mostly between 4 to 6 years old. Normally it starts as intermittent ecosystems. And then becomes basic. Normal control. This was the question. Divergency excess type. For those who were here on Tuesday, we were talking about vergence movements, do you remember? Opposite directions. So they move in opposite directions.
So when we say “Divergency,” what are we looking at? Are the eyes moving inwards or outwards? so this is an excessive, excessive movement towards the outside. Normally when do we see it? When they look at the distance, far away. And that’s when we have the angle is large at the distance. And can be it can be near. It can be straight, or it’s smaller than what it was in the distance. So normally the reason for this is a tight lateral rectus.
And respond very well to lateral rectus recession. Now people are starting to look, wait a second? And the question saws, “Resection.” But what is the difference? This is to loose it, and the other one is to tie it. Oh. Maybe we made a mistake on the question. The other type is convergence insufficiency.
So what is the meaning of that? And the distances are perfectly straight. But near, the eyes don’t pull in. So it’s a lot of weakness on the medial rectus. So how do we fix it? We have to tighten the medial rectus. That’s the problem. The problem is not in the lateral rectus. These are weak medial rectus.
Exercises? If you have a small angle, yes. It’s different when you have an angle which is 8 or 10 prism diopters, or you have an exotropia exercises may work. When you have a deviation which is more than 15% diopters, most likely it’s not going to work. So in the small angles, absolutely. Iso pushups. Now, realize I have a mistake on this. Because there’s no bilateral medial recess. It’s bilateral medial rectus resect. And I do apologize and for our and for everyone who is following in Cybersight, there is a mistake on this slide. It should say “Resection,” not” Recess.” We have the patterns as well. And that’s every pattern, the V or A, means oblique.
So we look in the primary position and looking up and looking down. And we can see how it’s straight in primary position. It’s straight in lower position. But when looking up, the eyes go outward. That’s why this is called a “V” pattern. And we can have an” A” pattern, which is the opposite. Today we’re going to do surgery of ecosystems with an “A” pattern. And today we’re going to do we’re going to look at the opposite.
Management of esotropia ecosystems. We can have non surgical, surgical. We can use Botox. And let’s look at signs of alarm which I’m going to tell you is the cross fixation.
Nonsurgical. Refraction, refraction, re, refraction. I can say it many, many times. No surgery must ever happen without you getting the proper glasses first. Let me give you an example. Let’s say that we take somebody who somebody who has plus 7 and has an esotropia of 45 prisms. And you very kindly accept to do the surgery. And then, after the surgery, the person needed glasses. So you decide to go for glasses. What’s going to happen?
So the person has the surgery done and then the glasses. The eyes are not going to be straight anymore. The eyes are going to be in a very large ecosystems. EX, not ET anymore. We have to be careful because sometimes we can have esotropia being up to 50% being fully accommodative. We have to be very careful about that.
However, 20% may compensate and may need surgery. Management, patching, patching, patching before surgery. Should we go why we should do these surgeries so little? Why? Because the ET can be persistent between 10 weeks and 6 months. And if we find two evaluations with ET greater than 40, this is not going to change. If the refractive error is less than 3, we may not need glasses either. But we need to do something. We have to be careful that the patient is not premature, low birth weight, syndromic, and developmental delay, paralytic incomitant, strabismus, as this one may change rapidly. So if the patient if the patient is with ET less than 3 and does not have one of these reasons, we should consider surgery. Fusion and stereopsis are absent before 2 months, but develop rapidly between 3 and 5. So we want to be sure that the kids are straight early in life.
So let’s go. Non surgical. Refractive error manage. Amblyopia management done. Bifocal glasses done, like in accommodative esotropia. Full time use of refractive correction. It’s been debated or accepted by some schools, others, not, the use of overminus or overplus lenses to control the high A C/A ratio.
After you have done all of this and nothing is working and everything persists, then you move to surgery. So you decided to do surgery. So now you have to decide. You can do medial rectus recess. You can do lateral rectal recess. You can do modal rectal resect, or lateral rectus reset. And either way esotropias or exotropias, your target is esotropia of 6 to 8 prisms after surgery.
So if you’re doing an ET, and let’s call it “ET,” you’ll always want a slightly under corrected. Because you don’t want that person to go outwards. It’s been proven. There are many studies that show if you have an esotropia of 6 in the first six months of life sorry my mistake in the first six months after surgery, that is going to stay stable over a very long time.
And the fusion, and this is enough to have good fusion. And the person doesn’t go in the opposite direction. When we are doing exotropias, XT, we want to overcorrect slightly. Because the tendency is always to drift outwards after surgery. So we want the person to look slightly overcorrected. 6 to 8. It’s clear.
Okay, so recessions. Recessions means recession means to make the muscle weak. So we want the muscle weak. The muscle is to too strong. So let’s make it weak. In this case, we are moving the muscle backwards. This is also an image from one from the book of one of my friends, a very good friend, his name is Dr. Scott Olitsky. And you want to give the credit because it’s a wonderful, fantastic diagram. And we have the the muscle has been moved backwards. So the muscle is not going to pull so hard.
That’s called, “Recession.” In Spanish we call it “recesion.” Recesion. It means we’re moving it back. So the muscle is not going to be as strong. You’re going to see today this procedure done several tombs. Okay? You’re going to see exactly this that being done today. We also we have two techniques. We can suture what it is. But sometimes sometimes this is too back. That is unsafe. But we just suture to the renal insertion and we just let it hang. That’s called hang back. So the muscle is hanging from the insertion. We can have what we call “Resection.” Because we are resecting a chunk of the muscle.
So we go to the insertion. We mark. And we are taking that piece of the muscle. We’re talking it. And we just suture back and move forward to the original insertion is what you do with your belt in your pants. You take a piece, but then you join the two ends. So that becomes strong. This is to strength. So this muscle is going to become stronger. And the previous one was going to was going to be weaker. The question the question is, if we can what do we do when we have deviations so large and so big that two muscles will not be enough? We call it supramax surgery. We can add more surgery to one given muscle, or the best thing to do is is add a third or sometimes even a fourth muscle. But we need to know, where do we want to move the eyes?
If the eyes are outwards, the lateral rectus has to be weakened. And the medial rectus has to be strengthening. If it’s the opposite, and we have oaths esotropias, the medial rectus need to be to be weaker and the lateral rectus need to be stronger. You can mix them. Sometimes you do two muscles in one eye and one in the other eye. Sometimes you do two muscles only in one eye. There are many, many ways to mix this.
One of the best signed to do Faden operation. Yeah. Faden operation, or posterior fixation suture is best done when rough an esotropia which is graded a near. A distance, it’s almost nothing, or very little. In a near you have a large esotropia. That’s when Faden operation works very well. Because Faden operation reduces increases the output conduct and reduces it slightly the power without changing the primary position. Okay.