MULTIPLE OPERATIONS FOR STRABISMUS

Transcription

1 Australian Journh of Ophthalmology. ( 1980). 8, pp ~ --- MULTIPLE OPERATIONS FOR STRABISMUS Graham Plttar D. 0. (LOND.), F.R.C.S. (ED), F.R.A.C.O. Ocular Motility Clinic Sydney ye Hospitat Summary Some examples will be noted where the strabismus surgeon plans the patient to have more than one operation Unfortunate/y most multistage sfrabrsmus procedures are unplanned and are a consequence of failure of the initial surgery The three most common causes of such failure wi/l be discussed B~ef mention will be made of the more important surgml techniques for rectus muscles that have had repeated operations Planned Multistage Strabismus Surgeiy The goal of strabismus surgery is to obtain the best possible result from the minimum number of surgical procedures. Occasionally one plans for a patient to have more than one operation as in the following cases ( 1) to avoid anterior segment ischaemia (2) Ciancia's syndrome (nystagmus blockage syndrome) (3) gross clinical signs in one eye possibly masking similar signs in the other eye (4) adjustable sutures. To Avoid Anterior Segment Ischnemia Operating upon 2 adjacent rectus muscles reduces the blood supply to that quadrant of the eye and related vascular defects of the iris can be demonstrated by fluorescein angiography.1 This probably has little if any clinical significance though McNeerZ issues a warning about simultaneous surgery on the lateral and superior rectus muscles particularly in adults who have had multiple previous operations. If 3 or more rectus muscles of one eye need to be detached from the globe then it is advisable to plan 2 separate operations with an interval of a few months. I have simultaneously moved 3 rectus muscles in children without ill effects but in adults this would be an unnecessary risk. Supposing that the right eye in an adult is significantly hypotropic and exotropic. The operation that is required depends upon the tightness of the right inferior rectus and right lateral rectus and the strength of the right superior rectus and right medial rectus. This information is obtained with the various forceps tests or their equivalent. Obtaining Hess charts and other orthoptic department reports is not helpful (a statement that applies to all strabismus work). In the example quoted (a) if the superior rectus is completely paralysed and the inferior rectus is not tight (an unlikely combination) then only one operation is necessary namely transposition of the horizontal recti at the same time correcting the exotropia (b) if the superior rectus is completely paralysed and the inferior rectus is tight then again the horizontal recti are transposed and the exotropia corrected and then after a wait of a few months the inferior rectus is rcessed on an adjustable suture (c) if the superior rectus has function Presented at the Annual Congress of the Royal Australian College of Ophthalmologists, Sydney, October 9th, Reprint Requests: Dr. Graham Pittar, 235 Macquarie Street, Sydney 2000 N.S.W. Australia. MULTIPLE OPERATIONS FOR STRABISMUS 15

2 then some combination of recession ' resection procedure is applied to the vertical muscles first. After a delay of a few months a similar procedure on the horizontal recti allows correction of the exotropia and also any residual vertical imbalance in the primary position. (2) Ciancir? S Svndrome" In this syndrome the patient has 2 uniocular null points of nystagmus. Each eye prefers to fix in adduction resulting in a face turn to the side of the fixing eye (hence another term for this condition is adduction fixation preference). Each eye has increasing nystagmus in both adduction and abduction from the null point.4 Being a uniocular problem uniocular surgery is suggested. The horizontal recti are recessed and resected in one eye while the other eye is occluded. Afterwards the new head turn is noted, one hopes this is nearly straii.ht, then the previously occluded eye receives the appropriate surgery which relates to the new head position. (3) Gross Clinical Signs in One Eve Possiblv Masking Similar Signs in the other. Dissociated vertical divergence and bilateral 4th nerve palsy are 2 important examples. If the clinical signs are grossly different in the 2 eyes then it is difficult to predict what will happen to the lesser affected eye after'the greater affected eye has had surgery. Clearly surgery must be conducted in stages and the patient made aware of this before the first operation. (4) Adjustuble Sit~irres This is a planned 2 stage procedure. The second operation is usually under topical anaesthesia within the first 24 hours of the original surgery.5 In young children more than one adjustment may be necessary under general anaesthesia. Unplanned Multistage Strabismirs Sirrgerv Unfortunately when a patient has more than one strabismus operation it is mostly a consequence of the first operation being unsuccessful. To obtain a hundred per cent success rate with any type of surgery is an impossible goal but ourduty must be to restrict the failures to an absolute minimum. In my experience the 3 most common causes of strabismus surgical failure are (A) ignoring the refractive error (B) failure to correct the tight muscle (and the associated tight conjunctiva) (C) improper management of inferior oblique overfunction. (A) Ignorance of the Refructive Error It is my opinion that the biggest single mistake that occurs in all of British Ophthalmology is failure to adequately correct the refractive error during management of strabismus. Children must wear glasses which contain the full atropine correction. One never "takes one or more dioptres off for the atiopine" and this statement applies to exotropes as well as esotropes if one is contemplating surgery. The operation aims. to cure only that deviation thal remains in the primary position when the glasses are in place and have been adequately worn. Failure to observe this simple rule frequent11 embarks the child on a whole series of unnecessary operations. In children there is no substitute for atropine LI discover the entire refractive error. In small children atropine ointment not drops must be used to avoid systemic overdose (the dry irritable flushed baby is not suffering from atropine allergy but from atropine poisioning). It is certainly worth prescribing any hyperme. tropic correction of one dioptre or more and these I glasses provide a convenient vehicle for press-on spheres and prisms in the all important postoperative period. It is essential that any hypermetropic anisometropia is corrected. This anisometropia was very likely the cause of the strabismus and it would be entirely unrealistic to ignore the cause of the problem. It is mandatory to correctly prescribe glasses for astigmatism particularly if uniocular. Even a quantity 0.5 dioptres is significant if the axis is oblique. One must also remember that this astit matism can alter significantly following ocular muscle surgery and the doctor must be prepared to re-refract when necessary. Finally one can predict the fusion potential and therefore if and how much surgery is required, 16 AUSTRALIAN JOURNAL OF OPHTHALMOLOGY

3 from observation of the refraction error (and observation of response to occlusion). The surgeon thus knows the diminished fusion potential available to the patient who has either hypermetropia of more than 4 dioptres or anisometropia (particularly if this is not myopic anisometropia). An orthoptic report would not be helpful and would not be available anyway in young children. (B) Failure to release the tight Muscle and Conjunctiva If for example a patient has a right lateral rectus paresis then in most instances with the passage of time the right medial rectus and its associated conjunctiva becomes contractured. If the patient subsequently requires surgery then surely the first priority must be to release these tight tissues on the medial side of the right eye. Clearly strengthening the right lateral rectus alone would be unproductive and weakening the overacting contra1,ateral medial rectus, which has so often been taught in the past, is obviously ridiculous. It is absolutely essential to understand that previous surgery is not necessary to create tight muscles and conjunctiva (though of course this can be a major factor). If an eye is for example esotropic for any length of time, for any reason, then the medial rectus and its conjunctiva will almost always become tight. If now in this example the medial rectus is recessed but the surgeon fails to, at the same time, recess the conjunctiva then the eye remains esotropic and what is worse, the medial rectus will again in time become tight in its new recessed position, when the muscle takes up the s1ack:even at this stage adequate surgery will straighten,the eyes in the primary position but one will surely reduce the full range of ocular movements. Forceps tests determine at surgery time if and how much conjunctival recession is required. A limbal incision is advisable. (C) Improper Management of Inferior Oblique Ove fiinction (i) Anomaly ignored. If there is significant inferior oblique overfunction then surgery is the only treatment possi- MlrLTlPLE OPERATIONS FOR STRABISMUS ble. This must be combined with whatever rectus muscle surgery is also required. It would be quite unfair to the patient for the doctor to programme two or more separate operations. (ii) Undercorrection of Inferior Oblique Overfunction Most surgeons prefer to myomectomise the inferior oblique and it is essential that all of the fibres are severed. The most common mistake is to leave untreated some of the posterior fibres of the muscle thus not curing the vertical component of the oblique dysfunction. This-broblem can be avoided by carefully searching for persisting fibres which can be found in the intermuscular membrane stretched between the two divided ends of the muscle. (iii) Overcorrection of Inferior Oblique Overfunction Overcorrection will occur if (a) the inferior oblique overfunction was of insufficient magnitude to warrant surgical interference. The surgeon must be aware of the clinical principles in this respect (b) if the antagonist superior oblique was not underacting. A common mistake is to weaken the inferior oblique when the overfunction is simply part of a tight lateral rectus syndrome when the antagonist superior oblique will also be found to be overfunctioning (c) if an adherance syndrome is produced (see below). (iv) Technical Complications of Inferior Oblique Myomectom y Most complications of inferior oblique myomectomy can be avoided by displaying the muscle to the direct vision of the surgeon. This is achieved by gently pulling the inter-muscular membrane towards the conjunctival incision and thus blind sweeping with the squint hook is unnecessary. It should be impossible to accidentally divide the inferior rectus and/or lateral rectus with this method. However the fat envelope of the globe is still very close to the squint hook even when the hook is correctly inserted behind the muscle. If this fat envelope is breached then an adherence syndrome6, can occur and this may be very difficult to treat. Surgical techniques for rectus muscles which have had repeated operations Only a brief discussion is possible for this paper. 17

4 Spring-Back Balance Tests7 This is an inti.a-operation test to assess the balance of mechanical forces influencing eye position. This position will of course be further modified upon the patient's recovery from anaesthetic and the consequent return of normal muscle tone. The surgeon after adequate mobilization of the globe allows the eye to spring-back to the central position from a. position of adduction and from a position of abduction. One compares not only the final resting positions of the eye but notes also the speed of this achievement, both factors being related and significant.8 Conjunctival Recession This has been mentioned previously and is almost always required for re-operations. Only 3 sutures are necessary for apposition of the conjunctiva and sclera. The exposed sclera is cleaned thoroughly with a weak cautery and an excellent cosmetic result is obtained when healing is completed in a few weeks. Marginal Myotom-v The principle of this procedure is that a recessed muscle can be further weakened without destroying a functional arc of contact with the globe. The first incision should be through 70 per cent of the width of the muscle. From the other side of the muscle a second adjacent incision is now made and enlarged gradually till the muscle is seen to have lengthened the desired amount. If the muscle needs to be relatively supra placed or infra placed then this can be regulated by'making the second incision exactly at the insertion. The surgeon must maintain some form of attachment to the proximal segment of the muscle in case all of the fibres are accidentally divided. Conjunctival recession is I think essential and mostly I prefer to use an adjustable traction suture (see below) on the opposite side of the eye to produce a temporary post-operative overcorrection. What has been described is the two incision Z myotomy. If this produces insufficient result then a third or more incision can be made i.e., a W myotomy. 18 Traction Suture Using 4 0 black silk (Ethicon K 581) a traction suture through the sclera and brought out onto the skin can be useful to adjust post-operative eye position.5 Mostly the traction suture augments the effect, or replaces the need, of a resected rectus muscle. Recently I have learned these sutures should always be made adjustable and hence a temporary bow knot is tied on the skin and the situation can be reviewed soon after surgery and then at weekly intervals up to 4 weeks following surgery. If for example after one week it appears that the suture is no longer necessary then the knot is loosened but not removed and the patient uses his eyes normally for a few hours before returning for reassessment. The knot may need to be tightened again and a similar procedure repeated one'week later. Leash of Synthetic Non Absorbable Material Occasionally material such as dacron tape can be used to limit movement of the globe in certain directions.9 If a patient has had repeated horizontal muscle surgery in one eye, movement of this eye, both to the left and the right, may be reduced. If unfortunately the patient prefers to fix with this relatively immobilised eye then the fellow eye will be overdriven in both left and right gaze (the swinging door syndrome). A dacron leash on the non fixing eye may overcome this gross cosmetic defect. Adjustable Sutures One should consider using adjustable sutures for the surgical treatment of all adult squints. This technique is particularly useful if there exists much scar tissue as a.result of multiple previous operations. In the past I have had experience using adjustable sutures for rectus muscle recessions but similar operations can be performed on resected rectus muscles, on transplanted rectus muscles10 and finally on the anterior fibres of the superior oblique muscle where torsion needs to be controlled.11 Conclusions It is seldom necessary for a patient to require more than one strabismus operation. AUSTRALIAN JOURNAL OF OPHTHALMOLOGY

5 Proper understanding of the problem before surgery can often prevent failure. Patients who have had multiple failed rectus muscle operations can almost always be surgically straightened in the primary position but ocular rotations are often diminished. References I Fells. 1. and,march. R. J. Anterior Segment Ischaemia following Surgery on Two Rectus Muscles. Strabismus. edited h$ Rcinecke. R. D. Grune and Stratton. New Yorh page McNeer: K. W. S\imposiuni on Smhismus. Transactions of the New Orleans Acadcmy of Ophthalmology Mosb?. St Loui\ page Cinncia. A. La Esotropia Limatcion Bilateral de la Ah- duccion en La Lacente. Arch. Ophth. (Buenoa Aires) Jnmpolshv. A. Symposium on Strabismus. Transaction of the New Orleans Academy of Ophthalmology. Mosby. St Louis page 43 I 5. Pittar. G. Adjustable Sutures for Squint Surgery. Australian Journal Opth. Volume 7. No. I. Feb Parkr. M. M. Symposium on Strabismus. Transactions of the New Orleans Academy of Ophthalmology. Mosby. St Louis page Jampolsky. A. Symposium on Strabismus. Transaction of the New Orleans Academy of Opthalmology. Mosby. St Louis page Rosenbaum. A. A. Jampolsky Fellows Meeting. Vail. Colorado. July (In Press). 9. Jampolsky. A. Symposium on Strabismus. Transactions of the New Orleans Academy of Oph!halmology. Mosby. St Louis page Carlwn. M. R. and Jampolsky. A. An Adjustable Transosition Procedure for Abduction Deficiences. American!ournal of Ophthal. 85: I I. Metz, H. Jampolsky Fellows Meeting. Vail. Colorado. July (In Press). MULTIPLE OPERATIONS FOR STRABISMUS 19