Reprinted from Hertle RW, Raab EL, Ing M, Helveston E. Infantile esotropia. J Pediatr Ophthalmol Strabismus. 2000;37(4):228-231.
Nelson: For this discussion, let us consider a case of infantile esotropia (Slide). A 4-month-old child presents with a history of his eyes turning in most of the time, since about 8 weeks of age. The child is healthy with an alternating esotropia for both distance and near fixation of 55 prism diopters (D). There is no A or V pattern, but there is a slight overaction of the right eye in the adducting position, trace inferior-oblique overaction, and no signs of dissociated vertical deviation (DVD). Ocular rotations are full otherwise. Cycloplegic retinoscopy is +1.25 D in each eye, and indirect ophthalmoscopy reveals a normal fundus in each eye. How would you manage this patient?
Hertle: Infantile esotropia syndrome, as we know, is one of the most severe disruptions of binocular function that can occur in human beings. It occurs during a sensitive period in both oculomotor as well as all the parallel processes of sensory development including, but not limited to, binocular vision or bifixation.
I think management of the patient includes management of the family. The most important thing I do when I see a child with this is to discuss the disease in lay terms to the families and to the parents of this child. For reasons we do not understand, this child did not develop binocular function when most children do in the first few months of life, and as a result of this anomaly, the child has a severely malfunctioning binocular system. With the current state of knowledge about the development of this condition and the known long-term effects of surgical and medical treatments, we know this child is in for a long and committed relationship with his or her ophthalmologist, and this is probably, in all likelihood, a lifelong problem. I believe treating these disorders while they are developing gives us the best opportunity to allow the brain to compensate for this anomaly.
I do not like to perform surgery at the first visit. I like to treat the child until I see a little bit of stability, or at least see the child twice. I also alternately occlude the eyes until surgery so the child does not develop a preference.
Helveston: There is nearly a 100% chance this child is going to need surgery. I would explain to the parents that patients who have large-angle esotropia persisting after 7 weeks of age have a virtually 100% chance of developing esotropia by 7 months of age. The earliest I would consider surgery would be at 4 months old. At that time, the child would meet the minimum criteria age-wise and historically. He or she would also meet the criteria for alternation and refractive error.
Ing: In my own practice, a patient who presents with esotropia is offered an opportunity to go into one of either two arms of a study we are conducting on alternate occlusion prior to surgical alignment to see if occlusion will favorably influence the binocular result. I would have a lengthy discussion with the parents as to whether they would like their child in the study. If they choose to enter their child in the study, the patient is randomized to either nonoccluding or alternating occlusion. He or she will undergo follow-up for at least 3 to 4 months. Our target date for surgery, in that group, is 8 months (±2 months).
Raab: If I am secure on the findings at age 4 months, I do not see a particular reason to wait further. I do not see many cases that early, but if I did, and the information was as good as I think I am going to get at the age of 6 months, I would proceed with surgery because I cannot think of a reason not to.
In this case, however, I am looking at soft things such as slight overelevation in adduction. Assuming there is no DVD and this is just a small overelevation in one eye, I might stall a little here. I am looking to take care of bilateral overaction or bilateral DVD. I do not think either of those are likely to develop by the age of 6 months, but I might be tempted for only that reason to hold on that long.
Nelson: If you feel strongly these children should have their eyes straight early, why not operate on them when you see them at 4 months?
Hertle: We need to be sure of the diagnosis. Although the diagnosis here is obvious, I would like to be sure of the deviation. We know that deviations up to 35 D can be intermittent. Therefore, I would like to make sure there is constancy over a 4-week period.
Nelson: What is the limit to where you would give a hyperopic correction at the time you first saw a child at 4 months of age?
Helveston: I believe surgical treatment of congenital esotropia falls into small, medium, and large, and if you try to cut it down much more than that you are fooling yourself. In my experience, children who develop esotropia related to hyperopia at under a year probably have congenital esotropia with a refractive component.
Nelson: Will earlier surgery generate better results for fine stereoacuity?
Ing: The question is should we be doing earlier surgery or having the patient less misaligned for less time. At this time, I do not think we can argue that surgery at 3 or 4 months of age will necessarily yield better fine stereoacuity. I feel gloomy about that because I studied 16 patients approximately 4 years ago and the mean age of alignment was 4.2 months. However, there was only one patient with fine stereoacuity and he was aligned at 2 months.
Nelson: What would be your surgical approach to this child?
Helveston: In the 1960s, there was an approximately 50% reoperation rate in congenital esotropia because of undercorrection. At that time, about 5 mm or 5.5 mm was generally considered the upper limit. In an effort to sort out some of the possibilities surgically, I decided to measure the distance from the limbus to the medial rectus insertion site - the range was 3 mm to 6 mm and the average was 4.4 mm.
I considered the maximum recession to be about 0.5 mm in front of the functional equator. For a full size eye, this turned out to be approximately 11.5 mm from the limbus. Arbitrarily, I deduced that 8.5 mm from the limbus would be the minimum recession and 11.5 mm the maximum. Take 0.5 mm or 1 mm off for children under a year. We were doing 5.5-mm recessions as our minimum, if you consider the medial rectus insertion was 3 mm. And so we made things topsy-turvy. We ended up going from 50% correction with one operation to 85% or almost 90%.
However, almost no one, including my residents and my colleagues, measures from the limbus. But I do. Therefore, I would do a bilateral medial rectus recession to 11 mm from the limbus.
Nelson: Do you ever, in terms of the technique of measuring from limbus, modify how far the insertion is from the limbus?
Helveston: Absolutely not. For years, I measured the insertion and then made a mental note, if not a note on the operative report, that I put it X mm from the limbus, which equals X-mm recession from the insertion. After we did the original, what I call validation study, I stopped doing it. It has become so ingrained in what I do that it is not something I would benefit from.
Hertle: My own preference is to begin with a large, 7-mm bilateral medial recession.
Raab: My reference point is the original insertion. I measure from the original insertion expecting, but not depending on, finding it at 3.5 mm to 4 mm from the limbus. I would do a 6.5-mm recession on each medial rectus.
Ing: I measure my recession from the insertion rather than the limbus, but I tend to be conservative as far as the numbers. Again, depending on the size of the eye and the age of the patient, I think there is some growth between 4 and 6 months of age than say 9 and 10 months of age, and so I take some of these factors into account in my mental computing.
Nelson: What about the possibility of accommodative esotropia after congenital esotropia?
Raab: There is a high likelihood of accommodative esotropia occurring after surgery regardless of whether there is a good first time result from the correction of the nonaccommodative esotropia.
Helveston: In my experience, 40% of our patients with true congenital or infantile esotropia who underwent surgery during the first 10 years required some correction of hyperopia. The correction is usually smaller. It is always under 5 D and sometimes it is as little as 2.5 D to 3 D. Often, this is just transient.
One of the things we do is explain to the patients in metaphor that children with congenital esotropia are like the boat out in the harbor with a small anchor. It does not take much of a tide to push it off. So, whereas a 2 D or 3 D hyperopia in an otherwise normally binocular child is going to be okay, in his or her case, it might not be okay.
Nelson: What is your experience in terms of accommodative esotropia following children who initially have congenital esotropia?
Ing: I tell the parents there are going to be a lot of pitfalls along the track. The eye might go up. The eye might go in again because of the need for glasses. I try to prepare them for a long period of treatment.
Nelson: You mentioned initially you believe these children do not function the same as other children. Can you elaborate?
Hertle: I am talking specifically about psychophysical tests of visual function. They do not bifixate. I think bifixation is extremely rare. All doctors can remember the one patient out of hundreds or thousands who did have bifixation. There really is something different visually and functionally both from an afferent and efferent point of view in these patients.
Also, we have been involved in studying the oculomotor systems of infantile esotropes from infancy all the way through to the seventh or eighth decade, and not one of these patients has a normal oculomotor system checking smooth pursuit, saccades, and stability of oculomotor fixation. There are actually oculomotor markers for the onset of binocular disruptions within the first year of life. Again, this condition is a severe oculomotor function disruption.
Helveston: These children are not normal in their binocularity. They do not have the proper biofeedback antidiplopia mechanism, which, for antidiplopia, means keeping both foveae on the object of regard. I remind the family these children operate under a retinal-rivalry situation. Binocularity does not mean simultaneous use of the entire retina in both eyes, it means rapid alternation.
However, either related to the timing of surgery, or possibly to some innate characteristics of the children themselves, they may be able to develop better binocularity. I think quite strongly, and I try to relay this to families, that timely, good motor alignment is something that is dependent on skill at surgery and persistence, but the level of binocularity may be related to the innate ability of the child. Stepping back, I think you have to be a bit humble in the management. If you are a good surgeon and you can move the medial recti back and do the other things you need to do, then I think there are higher powers that are going to determine binocularity.