Lecture: True Ocular Muscle Transplantation to Treat Extra Large Horizontal Strabismus

[Adedayo] Hello, everyone. We’ll be talking about true ocular transplantation surgery for extra large horizontal squints, our experience in Africa. My name is Adedayo Adio. I don’t have any financial disclosures. I work at the University of Port Harcourt Teaching Hospital. And I’m the current chairperson of NIPOSS which is the society of all pediatric ophthalmologists in Nigeria committed to ensuring the overall eye health of the Nigerian child.

By way of introduction, the term strabismus is derived from the Greek word strabismos to squint, to look obliquely, and means ocular misalignment. The misalignment may be caused by abnormalities in binocular vision or by anomalies of neuromuscular control of ocular motility. And it could manifest or latent.

We have some patients here with infantile esotropia, manifest one. Infantile exotropia. And some patients with squints of acquired or organic origin. We know that sensory exotropia can develop as a result of any condition that severely reduces vision, or the visual field in one eye, and it can develop in older children or adults with one poorly seeing eye. And also infants or young children with blind or poorly seeing eyes usually develop esotropia. But adults usually develop exotropia.

Now this could be comitance or concomitance or incomitance or concomitant. A quick explanation of this. Where the size of the deviation is the same in all directions of gaze and there is no limitation of ocular movement, and therefore nor abnormal head posture, that is what we call comitant or concomitant. And where the size of the deviation varies depending on the direction of gaze and there is limitation of extraocular muscle movements. That is what we refer to as incomitant or noncomitant. And in this situation the secondary angle of the vision is usually greater than the primary division depending on the eye you’re using to measure your size of your squints.

The impact of squints on the patients usually if it persists and is not treated, the patient can lose vision, can lose binocularity or may not even acquire it, may have double vision. And in a society may be stigmatized and there is also the possibility, according to many studies, of multiple corrective surgeries within the lifespan of the individual. Usually squint surgery is about 60-80% success rate and in a study by Kumari said 83%, Lajmi said about 78%. And we find that this surgery may even require to be repeated about 2.1 times to achieve 74.4% success rate. That possibility is there for multiple corrective surgeries.

In treating squints, the various options are available I have shown here on this slide. You can use glasses, you can offer orthoptic exercises, you can give botox, or offer extraocular muscle surgery to the patient which could include recession or resection. In recession, because some of our audience are also probably involved in orthoptics, the muscle is moved towards the origin so as to weaken it. And in resection, a piece of the muscle is removed and the remaining stump of the muscle is moved to the insertion to strengthen the muscle.

Generally, you do not want to waste too much time in treating squints, you should treat it quite early.

And to do this tables and dosage charts based on the size of the preoperative deviation. And usually use eyeglass single or the other type of prism bar to be able to measure the squints. Now the tables that are available to measure to be able to know what dose of surgery to do, are a bit limited. This is the one for esotropia. And this is one for exotropia. You will see that they are not able to handle very large squints.

And these sorts of tables are usually useful for only those that are operated upon early as obtained in developed countries. But here in Africa, or in developing countries, squint patients do not commonly present early here. The mean age of presentation according to a study that was done by Mvogo is 17 years. Some squints are usually so large that you even have to operate on all four horizontal muscles at the same time. And some may not even be fully corrected even if you work on all of the four maximally. And therefore you risk under correction.

Any delay in treatment, which often obtains in developing countries, the size of the deviation becomes extremely large and the amount of surgical dosage required becomes significantly more than what the charts can handle.

I’ll show you some pictures of some neglected squints that have been allowed to grow so large that you can’t even see the sclera at the edge of the weaker eye, the deviating eye.

What is a large squint? Any squint that is up to between 50-70 prism diopters is large. And what is an extra large or super large squint? Any one that is greater than 70 prism diopters is super or extra large. A very large angle of deviation of more than 70PD may not be easily treated by using minimum surgery, two horizontal muscle surgery. One has to operate at least on all or three of the horizontal muscles.

And we know the problems of operating on all muscles, the four muscles there. We have anterior segment ischemia, the surgery will necessarily be lengthy, there’s an increased risk of infection with staying long at the operating table, prolonged anesthesia is also there, particularly the younger the patient. And if you do more than the standard dosages, we have the risk of duction limitation. That means you can induce incomitance. In large recessions this can cause widening of the palpebral fissure and when you do large resections it can become narrower. If you’re operating on only one eye, the difference is visually very much obvious.

And one of the reasons for late presentation. Most patients present late because of ignorance, they’re not aware of the fact that this can be done. Some people think that is just the way their face, they were born that way so they want to remain that way. Or they don’t know what to do about it. The other one is poverty. Sometimes because of few specialists, these surgeries are usually very expensive and because of the high rates of tariff in importing materials, most developing countries do not produce some of the materials that are used for this surgery. It’s usually expensive so poverty is one of the reasons for late presentation. And then, of course, lack of skill and very few specialists available to perform this surgery.

Also the surgical techniques that are available for extra large squints are listed here. Very large recess/resect which has its own problems, we have Hangback method where sutures are used to simulate an extra weakening or extra effect. Then silicon expanders also, especially if the squint is comitant. And if it is incomitant, usually they can also want to perform transpositions and cut the muscle to the periosteum.

But this has been found to be inadequate for some of the squints that are seen in developing countries. There was a need to develop a surgical procedure that will allow for lengthening of the muscle. And this has been seen or studied by other workers by Jethani et al, Kaur, and Choudhary et al. The issues with using synthetic materials are also very evident like the silicone or any of the other materials like sutures, the muscle can insert or reinsert anywhere else instead of the intended spot where you placed it. Sutures can break, or can be not around where it’s intended where it should be, and there could also be excessive inflammatory response.

True muscle transplantation technique the concept of it was developed and was found to be required. And studies are, like I said, have proven the effectiveness of transplanted ocular muscle in terms of correction of deviation.

It’s always best to use what is already there instead of bringing in something foreign into the body. Usually when we do a resection we discard the muscle that is resected. So why not after we resect it, join it, and then recess the new longer muscle.

But this is something that has been used in other areas in other surgical dissections as studied by Bostwick and Bruckner. Usually can offer the patient that has had the breast removed in mastectomy by using the latissimus dorsi flap. This is a broad flat muscle, that is the latissimus dorsi, that supplies the majority of the lower posterior thorax. Also another form of muscle transplantation a slender muscle located in the media compartment of the thigh. The other adductor muscle in that area we have the adductor longus, the adductor brevis, magnus, and the pectoral muscles. The gracilis is the most superficial deep adductor that overlies this remaining muscle. This muscle can be harvested in cases of facial paralysis to reconstruct a smile. It can also be used in cases of Moebius syndrome where the muscles are not able to allow the patient to smile.

The following are indications for true ocular muscle transplantation. Very large squints that are larger than 70 prism diopters, previous surgery that does not fully correct the deviation. And then when the patient does not want the seeing eye like in cases of sensory deviations, they only want that surgery done on the amblyopic or the blind eye.

I was able to perform the first one in Nigeria here in the University of Port Harcourt Teaching Hospital where I work three years ago, after which a number of others have been done. And I’m in the process of teaching others. What we find is that the effect on the medial rectus is more because you can get more muscle from the lateral rectus.

Without wasting too much time, I’m going on to the surgical procedure where I’ll be talking about and show you an animation first, like a cartoon, and then I’ll be showing you some pictures so that you can catch a clear glimpse of different ways you can do this same procedure, and then I will show you a video at the end. After a routine cleansing and draping, for instance you want to do muscle transplantation for extensive exotropia. For example the vision has 80-85 prism diopters exotropia. Your plan will be to a lateral rectus recession of nine millimeters and a medial rectus resection of seven millimeters. But what you want to do is to transplant five millimeters of the resected medial rectus to the lateral rectus in the less dominant eye. Here we’re using the right eye.

I’ll show you a table that was published by Pineles and Kekunnaya et al in their paper about guidelines. So you can use these guidelines for surgical dosage for transplantation of extraocular muscles depending on the size of your squint.

On average, you can find about a millimeter of transplanted muscle gives up to 4-5 millimeter additional effect. But it is important to know that when you’ve taken this muscle, don’t cauterize, just clamp it a little bit, then you cut, you keep it in saline until you want to use it.

This picture is showing the muscles being isolated. Now the plan, like I said, is to do lateral rectus recession of nine and MR resection of seven, that will give you about 50 prism diopters and that extra five millimeters will give you 20-25 extra and that will help us be able to correct the deviation.

In this patient, in this cartoon, seven millimeter MR resection was planned. And then you resect it, and take five millimeters of the seven millimeters that was resected to transplant it to the lateral rectus that you want to weaken or recess. This is what is representing that. The remaining medial rectus should complete the resection of strengthening surgery which is tied to the original inserted. And then you move your transplantable segment of medial rectus to the lateral rectus that you may have disinserted. That is one way to do it, you may disinsert it before you attach the five millimeter segment that you’re transplanting. Or you may, I will show you another method towards the end.

Also, this is the extraocular muscle that has been removed from the medial rectus in the process of resecting it and then you move it to the lateral rectus to be sutured, to lengthen that muscle.

Like I said, you switch out the remaining medial rectus back to the original insertion where it was with 5.5 millimeters and then that is the segments there that it isolated.

Once you attach it to the lateral rectus, it’s now lengthened by a further five millimeter and that will help us to be able to achieve what we are trying to achieve. Transplantation surgery is completed and the free end of the newly added muscle, you make sure you suture it securely through the lateral rectus. You now move the insertion back by nine millimeters, which was our plan.

Here this is the segment of transplanted medial rectus that we want to transplant to the lateral rectus. You make sure you attach it to the end of the lateral rectus that in this instance was disinserted before transplantation. And then you move it back nine millimeters beyond the insertion and you take six suture bites to the sclera. And there that is the completed process there.

There’s a short video. After a routine cleansing and draping, you now hook the medial rectus muscle here, you secure it properly. You ensure that the entire segment of the medial rectus was picked up by your hooks. Then to check the medial rectus to be able to secure the segment of transplantable medial rectus, you make sure that you imbricate the muscle near the insertion. That is what is happening here. Just the same way you suture when you’re doing your resection or you’re doing your recession, you first of all take that near the insertion. Remember this is the muscle that we want to resect, we’re taking the extra bit of muscle that we want to transplant. And then you measure your seven millimeters and then you also suture at the point where the seven millimeters segment has been measured. I’m using a 6-0 double ended Vicryl that’s partially blue, we’ll take partial thickness and full thickness bites after a central bite was taken. And then you ensure that you make sure that you don’t puncture the sclera while you’re doing your passing of your needles through. And you take a locking bite, yes.

Point of the seven millimeters and then you also what you’re going to transplant the segment of medial rectus that you want to transplant. And then you complete your resection by moving the remaining stump of the medial rectus back into the original insertion and this will strengthen that muscle.

This is very good for those who want to have just one eye surgery done. In that same eye you can have all of your surgeries done and then you make sure that you securely fix your muscle there so that it doesn’t stretch. And then you do your pull test when you’re done and remove your Moody forceps after you cut your sutures. Right, that is the end of the medial rectus resection. And we have a thing of the transplanted segment.

And then we move on to the lateral rectus resection. I usually use a fundus-based incision which is more cosmetic. Some people use a limbus-based. Then you locate your lateral rectus muscle. You ensure that you pick up the entire width of the lateral rectus muscle. To know whether you have picked up your entire lateral rectus muscle, you try and push toward the limbus, your hook, if it goes easily then you have hooked everything. And I also do a pull test to be sure that you’ve picked up everything on the two sides. You can check and remove all intramuscular center to be sure that the whole segment of muscle has been picked up.

And then in this ways, another method you can use you may not completely, you may not even distance that. You can switch on this transplanted segment directly onto this still inserted lateral rectus that is insertion which is the method that I’m using here. You do whatever is convenient for you, you can disinsert the lateral rectus and then you suture at the ends. Or you can suture where it is still attached and then you disinsert when you’re done. The important thing is you correct properly and then you make sure it is properly aligned and able to lengthen your muscle. And for each millimeter of this muscle you can correct up to four to five prism diopters of deviation.

Sometimes it’s more comfortable for you to completely remove the lateral rectus and then you attach the muscle. Here I’m attaching the Moody forceps so that you can know exactly where the inferior end of the lateral rectus was and then you attach at the other other, the superior end, and then you complete your disinsertion. And there you have your muscle completely sutured. And then if you have some areas that you think is not properly attached, then you make sure you attach it properly. And then you can put your Bahby forceps, should be able to, you can see the muscle there lengthed. The Bahby forceps will hold back the lateral rectus while you’re preparing the sclera for affixed sclera bites the process of weakening the lateral rectus.

We plan to do nine millimeter, you use your calipast to measure it. Some people use gentian violet to keep it there, to be able to remember where the sutures. You can just lightly depress the sclera there. You have to be careful because at this point for the back, you’re working over the macula, almost working above the macula. You dare not puncture anything there, you have to be careful with partial thickness, keep checking to be sure because where the end of the needle comes out, that is actually where your muscle is attached. Right. Then because it’s a bit slack you may need to push it back and then you tie your sutures, you check using the pull test again, is it properly secured? If it is you can cut your suture, remove your Moody and then maintain homeostasis if you wish. And then you can now close the sclera. And then the patient is good to go.

This was the patient’s first day postop with the eyes well aligned. And this was the patient six weeks postoperative. What will be the complications? You could lose muscle, especially if you are working on the medial rectus. If you did not suture it properly you can have a problem with the medial rectus. And we all know that that is one muscle that we never lose. You could also have new deviations if you don’t center your muscle properly or unintentionally do insert one muscle a little bit one end of the muscle behind or in front of where you want to put it before. You could overcorrect if you don’t take the exact segment that is required for that deviation. For instance, you resect several millimeters and then you transplant several millimeters, it’s going to give you something that you do not really plan for. And then we could have infections also and that will happen.

What happens with the transplanted muscle? It has been found by Hiatt who studied this in 1973, that this muscle survives and remains viable. However, it undergoes changes, necrosis and the capillaries could be obliterated with gradual fibrous replacement of these muscle fibers within a month. But it has been found not to incite as much reaction from recipient muscle or sclera. And the tensile strength correlates very well to repaired muscle wounds. And after 14 days, there is good union of the transplanted muscle to the sclera and to the recipient muscle.

I’ll show you some pre op and post op pictures. We find that even in children this works quite nicely for those who have extremely large squints that are off the charts. And I’m showing you some of those patients, see the deviation and then the post op. And it’s very popular among the ladies, particularly if they have one blind eye. We have quite a number of those young ladies coming in with sensory exotropia. And then this is very good surgery for them, they have that surgery in just one eye. You can also have it in both eyes depending on if you need to take a muscle, do one of the muscles in the other eye, you don’t have to do all four muscles. Maximum of three and you’re good to go.

This is a patient that had up to a hundred prism diopters and she healed quite nicely.

I’ll share with you some of the outcome of the patients that we have done over time. A successful outcome was defined as a postoperative angle of deviation within 10 prism diopters of orthophoria at about six months postoperatively. I included 10 patients in this write up. Eight with exotropia, four of them were children. We collected them through a period of two years. Mean age was 18 years, that shows you that people don’t really present on time. And male/female ratio was 1:1.5.

The mean preoperative deviation was 90.5 prism diopters for distance and 90 prism diopters for near. All the patients underwent four preoperative orthoptic check up and refraction. The patients were followed up on day one, day 30, and six months. All the patients underwent standard muscle transplantation technique like I described where they resected extra stump of rectus muscle was transplanted to the other rectus using 6-0 Vicryl double ended sutures using standard technique. Some who used nylon or mersilene sutures but I find in my hands that Vicryl still does the same job.

You’ll find that most of the patients in this slide had quite good vision in logMAR and the stereopsis was very poor and we find that the outcome was quite good. Deviation collapsed to a mean of about six prism diopters six weeks after and 2.5 prism diopters six months postoperative for these patients. And most of those who had esotropia, all of them were orthotropic. There were no duction limitations in any of the patients though it is a small group. The overall percentage of success was 90% after six months of follow-up.

I’ll ask you to think about the advantages of this technique. It’s physiologic, you don’t need to introduce any foreign elements, nothing is wasted. The muscle that was previously thrown away now you can use, the surgery on the dominant eye can also be avoided. And there’s better preservation of the ductions as opposed to when you are doing very large recessions when you might find that the patient will not be able to look completely to the very end. And it’s a simple learning curve, you’re more likely to have just one procedure when this is done, you’ve done your due diligence, you measure accurately and you plan very well.

In conclusion, true ocular muscle transplantation is a safe option for extra large squints among Africans. The surgical results are stable in long term, even in children, and therefore it is a very viable option for us here in Africa and in other developing countries.

And of course, mothers when their children have large squints and it’s taken care of, they’re very happy. Husbands also very happy. Happy wife, happy husband. And of course the surgeon also, very happy. Thank you very much for being with me.