Experts’ opinion – Case 5

In addition to answering the questions posed to our members, our Experts were also asked the following questions :
1) Assuming this strabismus is caused by mechanical factors, how would you explain the cyclic presentation?
2) Could you please let us know whether or not you feel there would be a conflict between different pathogenic theories & could you give us an explanation for the same?

Dr. Linda Dagi

1) Which eye would you operate on : (a) The non-dominant eye / (b) Both eyes?
I assume the question pertains to the first surgical plan. Both eyes have excellent acuity and there was little evidence of incomitance at pre-operative evaluation. However as the patient’s right eye was typically the esotropic one, and as the syndrome findings were present in the right eye only, I would have done surgery on the right eye.
(2) Do you feel recommending orbital image studies prior to the surgical procedures in highly myopic strabismus is : (a) Indispensable, (b) Useful but not indispensable / (c) I would not recommend prior image studies because muscle path found at surgery is the key to the surgical plan?
Orbital imaging is useful but not indispensable. It helps with surgical planning, and can confirm both the diagnosis and the degree of displacement of the involved muscles. It can also warn the surgeon about a significant posterior staphyloma, and can help rule out thyroid eye disease- although the latter is usually easy to distinguish based on the clinical presentation.
If I were working in a setting with more limited access to high resolution orbital MRI, I would probably manage without the MRI and depend on intra-operative findings. I would not choose CT as I do not think it is worth subjecting the patient to the associated radiation. Finally the surgeon should expect that repositioning of the muscle paths reduces the esotropia (and hypotropia if present) during the procedure. If this is not noted intra-operatively, there may be less benefit than anticipated. In such a case (not in the case presented here) the altered muscle paths may not be contributing very much to the strabismus seen.
(3) Which approach would you choose in a downward shift lateral rectus (LR) muscle in cases with no vertical deviation : (a) Resection or plication of the LR, (b) Repositioning the LR muscle belly by a myoscleropexia, (c) Resection with myoscleropexia of the LR, (d) Harada technique, (e) Yokoyama technique / (f) Other?
My favored choice would be the Yokoyama technique. I find it very forgiving, and unlikely to induce a vertical deviation where none exists. A small resection with myoscleropexi is not unreasonable, depending on the degree of esotropia. In either case I would likely place the medial rectus on an adjustable suture and recess, or maintain the option to recess, unless the pre-operative deviation is very modest.
(4) Assuming this strabismus is caused by mechanical factors, how would you explain the cyclic presentation?
The cyclic nature may result from variable slippage of the LR downward as the LR-SR band is slowing degenerating. Once the degeneration is complete, the esotropia will become less or non- intermittent.
(5) Could you please let us know whether or not you feel there would be a conflict between different pathogenic theories & could you give us an explanation for the same?
The pathogenesis likely is related to a combination of degeneration of the LR-SR band and protrusion of the globe through the muscle cone caused by elongation, and staphylomatous supero-temporal enlargement, of the highly myopic globe. I do not think there is a conflict between these theories. They both contribute. In “sagging eye syndrome” there is little more than loss of integrity of the LR-SR band with secondary muscle slippage. With high myopia, a varying degree of shift of the globe out of the muscle cone associated with globe enlargement and staphylomatous change is likely enhanced by poor LR-SR band integrity. This loss of integrity probably occurs with growth of the globe and is aggravated by aging. For this reason it is relatively rare to see strabismus fixus in the young high myope; the disorder itself is progressive, even after the degree of myopia seems not to have changed.

 

Dr. Vincent Paris

Dr. Paris feels this is a fantastic case for many reasons; (i) Cyclic strabismus in adult with typical eso linked to high myopia (ii) Postop = preop within few months (iii) Looking at all the pulleys, even in vertical muscle and action on this without induced undesirable vertical or torsional postop deviation & (iv) The amount of surgery of the second procedure is twice more than performed in the first one.
He also made a few comments & / observations WRT the case :
(i) We cannot think strabismus only in terms of cover test. Brain control is the key. That’s because we can have cases with postoperative deviation curiously equal to the preop, not poorly reduced but equal as, disregarding our mechanical action, the brain would decide to maintain the eyes in such position. It is the case in true convergence insufficiency cases.
(ii) I never fix my surgical plan before testing the elongation of the muscles, looking at the eye positions under GA with full curarization and looking at the pulleys especially in cases when these pulleys can be involved (alphabetic pattern, high myopia, trauma, etc.) but in this case I wouldn’t perform any translation of the SR , fearing to induce torsion.
(iii) You didn’t ask another classical question : Adjustable?
Probably not; in these cases especially when we expect finding such pulley abnormalities which can more easily observed and treated under GA but when experience is growing you can do it also under topical anesthesia.
His replies were as follows :
(1) Which eye would you operate on : (a) The non-dominant eye / (b) Both eyes?
Depends on the position of each eye under GA, if both eso I would perform bilaterally; in these type of cases it is usually the case. As a secondary response I think that strabismus surgery in horizontal deviation has not only to choose between the side of the surgery but the muscle to operate. Here I would be focused on the LR (as I do in esophoria in the fourth age when LR and its pulley are also involved).
One interesting point; you got a good result with only 6 mm of surgery in the first step compared with 15 mm in the second step in the other eye where no abnormal pulley was found. Your action on the LR reinforced the horizontal vector of action of the LR which is indeed crucial for the long term result of that type of pathology.
(2) Do you feel recommending orbital image studies prior to the surgical procedures in highly myopic strabismus is : (a) Indispensable, (b) Useful but not indispensable / (c) I would not recommend prior image studies because muscle path found at surgery is the key to the surgical plan?
I believe only on what I really see as a surgeon facing the eyes positions and the muscle direction and elongation. I rarely use MRI (Grave disease excepted of course). I think that duction test is not enough and has to be systematically completed by elongation test, both tests give complementary information.
(3) Which approach would you choose in a downward shift lateral rectus (LR) muscle in cases with no vertical deviation : (a) Resection or plication of the LR, (b) Repositioning the LR muscle belly by a myoscleropexia, (c) Resection with myoscleropexia of the LR, (d) Harada technique, (e) Yokoyama technique / (f) Other?
I stopped resection 25 years ago, prefer plication. So plication and myoscleropexia
Questions (4) Assuming this strabismus is caused by mechanical factors, how would you explain the cyclic presentation? & (5) Could you please let us know whether or not you feel there would be a conflict between different pathogenic theories & could you give us an explanation for the same?
We cannot think strabismus only in terms of cover test. Brain control is the key. That’s because we can have cases with postoperative deviation curiously equal to the preop, not poorly reduced but equal as, disregarding our mechanical action, the brain would decide to maintain the eyes in such position. It is the case in true convergence insufficiency cases. I remember a case of twin brothers with cyclic eso one was squinting a day, his brother the day after !! Never published but one colleague told me that he met such a case too!!

 

Dr. Jan Willem Pott

(1) Which eye would you operate on : (a) The non-dominant eye / (b) Both eyes?
I would operate on both eyes. I would manage this case as a case of cyclic esotropia, and in these cases I will always operate on two eyes.
(2) Do you feel recommending orbital image studies prior to the surgical procedures in highly myopic strabismus is : (a) Indispensable, (b) Useful but not indispensable / (c) I would not recommend prior image studies because muscle path found at surgery is the key to the surgical plan?
As cases of mechanical strabismus in high myopia are fairly rare, I still do MRI imaging in these patients. Moreover, these studies have a good accessibility in my hospital, and they help me in planning surgery and explaining to the patient what I will do; but, I can imagine that in areas where these patients have a more frequent presentation, or where imaging is not available, that you could perform surgeries of this kind without preoperative imaging.
(3) Which approach would you choose in a downward shift lateral rectus (LR) muscle in cases with no vertical deviation : (a) Resection or plication of the LR, (b) Repositioning the LR muscle belly by a myoscleropexia, (c) Resection with myoscleropexia of the LR, (d) Harada technique, (e) Yokoyama technique / (f) Other?
Under the presumption that we are dealing with a strabismus fixus, with mechanical restriction due to the abnormal path of the extraocular muscles I would go for the Yokoyama technique. The case presented however does not fit to that definition in my opinion, as there is no restricted eye movement, or abnormal forced duction test. So here I would only correct the strabismus angle with a resection on the lateral rectus muscle.
Questions (4) Assuming this strabismus is caused by mechanical factors, how would you explain the cyclic presentation? & (5) Could you please let us know whether or not you feel there would be a conflict between different pathogenic theories & could you give us an explanation for the same?
Cyclic esotropia is a rare phenomenon, where we do not know the cause. There are numerous case reports presuming to give some clue to the cause, but in the end we still don’t know what is going on. As I have stated earlier, my approach to this case would be to deal with this patient as a case of cyclic esotropia, and not concern about the high myopia or slightly abnormal pathway of the rectus muscles. This is under the presumption that there are no limitations of ductions and no abnormalities on forced duction under anesthesia, which was the case in the presented patient. The same goes for any pattern deviation we sometime see in cyclic esotropia. Especially, V pattern and elevation in adduction are common in cyclic esotropia. But these patterns will disappear when fusion is restored by simple operation on the horizontal muscles. So my advice would be to keep it simple; restore binocular function in the easiest way possible.

 

Dr. T. Surendran

1) Which eye would you operate on (a) The non-dominant eye / (b) Both eyes?
I would operate on the non-dominant eye
(2) Do you feel recommending orbital image studies prior to the surgical procedures in highly myopic strabismus is : (a) Indispensable, (b) Useful but not indispensable / (c) I would not recommend prior image studies because muscle path found at surgery is the key to the surgical plan?
I feel recommending orbital image studies prior to the surgical procedures in highly myopic strabismus is Useful but not indispensable
(3) Which approach would you choose in a downward shift lateral rectus (LR) muscle in cases with no vertical deviation : (a) Resection or plication of the LR, (b) Repositioning the LR muscle belly by a myoscleropexia, (c) Resection with myoscleropexia of the LR, (d) Harada technique, (e) Yokoyama technique / (f) Other?
I would choose a Resection or plication of the LR
(4) Assuming this strabismus is caused by mechanical factors, how would you explain the cyclic presentation?
I feel this esotropia is essentially an adult onset cyclic esotropia, with the mechanical component being doubtful or just incidental. Adult onset cyclic esotropia is rare, but cases have been reported in luterature. Adult onset cyclic strabismus can occur due to many causes of which high myopia is also described. A neuroimaging to rule out more dangerous disorders like brain stem lesions should be done. Heavy eye syndrome, in contrast, is also a differential in these patients with the mentioned findings on imaging. But the age of onset and the recurring nature of disease points against this diagnosis.(5) Could you please let us know whether or not you feel there would be a conflict between different pathogenic theories & could you give us an explanation for the same?
Yes, there is definitely a close call between myopic pathology versus cyclic etiology, but due to the aforementioned reasons, I would again mention that this could be a case of primary cyclic esotropia.

 

Dr. Tsuranu Yokoyama

1) Which eye would you operate on : (a) The non-dominant eye / (b) Both eyes?
Neither (a) nor (b). I do union of the superior and lateral rectus muscles (Yokoyama procedure) only on affected eye(s). In this case, if displacements of the rectus muscles exist only in the right eye, I would perform a union surgery only on the right eye. This procedure is effective only on strabismus caused by displacements of the superior and lateral rectus muscles and not effective at all on concomitant esotropia.
(2) Do you feel recommending orbital image studies prior to the surgical procedures in highly myopic strabismus is : (a) Indispensable, (b) Useful but not indispensable / (c) I would not recommend prior image studies because muscle path found at surgery is the key to the surgical plan?
I feel recommending an orbital image study prior to the surgical procedures in highly myopic strabismus is Indispensable. This patient has high myopia and possibly concomitant esotropia, and its exact cause would be unknown without an imaging study prior to surgery. I do not entirely rely on intraoperative findings because they may vary with a slight rotation of the globe by control sutures.
3) Which approach would you choose in a downward shift lateral rectus (LR) muscle in cases with no vertical deviation : (a) Resection or plication of the LR, (b) Repositioning the LR muscle belly by a myoscleropexia, (c) Resection with myoscleropexia of the LR, (d) Harada technique, (e) Yokoyama technique / (f) Other?
I would choose the Yokoyama technique. I have done this procedure on a number of mild myopic strabismic patients in which downward shift of the LR was confirmed by MR imaging but vertical deviation was not found. Even restriction in abduction was unobtrusive in some cases. They might have been misdiagnosed with concomitant esotropia without imaging studies. The only reason I recorded their MRI was that they had both high myopia and esotropia.
Questions (4) Assuming this strabismus is caused by mechanical factors, how would you explain the cyclic presentation? & (5) Could you please let us know whether or not you feel there would be a conflict between different pathogenic theories & could you give us an explanation for the same?
My explanation is simple. This patient has both myopic (mechanical) strabismus AND concomitant esotropia. The cyclic nature of this patient’s esotropia can be ascribed to concomitant esotropia. I do not think myopic strabismus causes cyclic strabismus because its deviation angle is almost always constant.

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