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Surgical Management of Exotropia*
SURGICAL MANAGEMENT O F EXOTROPIA* ARTHUR JAMPOLSKY, M.D. San Francisco, California
For the purposes of this presentation, exo tropia will be considered as a constant rela tive divergence of the visual axes for any given fixation distance. This is by way of contrast to exophoria and intermittent exo tropia. It is the element of constancy which differentiates the problem under discussion from the latter two instances. Patients with constant exotropia exhibit the most profound sensory- motor anomalies. Constant exotropia is the last stage of a pro gressive disease process. It is of interest to note that one does not see infants with constant exotropia, except in bizarre in stances. Visual infants (under six years of age) may exhibit a constant exotropia only in later years, and as a rule do not develop the con stancy until after the age of six years. The surgical management of constant exotropia, therefore, is primarily concerned with visual adults, who possess less adapt ability of the sensory mechanisms. Since all constant exotropes have passed through the earlier stages of exophoria and intermittent exotropia, it is paradoxical that they all have experienced good binocular fusion, while at the same time have de veloped a most profound sensory suppres sion and secondary motor defects. It will be the purpose of this paper to point out the sensory and motor defects asso ciated with constant monocular and constant alternating exotropia, and, by example, to show the surgical steps directed at affecting both the sensory and motor aspects of the problem. What are the sensory-motor defects in constant exotropia? Hemiretinal regional * From the Department of Surgery (Ophthal mology), Stanford University School of Medicine. Presented at the V I I Congress of the Pan-Pacific Surgical Association, Honolulu, November 14-22, 1957.
suppression is large in extent and deep. Monocular amblyopes characteristically have a "built-in" suppression. That is, it is usual to be able to account for an over-all blur of the retinal image in one eye by a significant amount of anisometropia, a corneal scar, lens opacity, or some similar such phenomenon. With such "ready-made" suppression it is not necessary for the sensory mechanism to make such a marked adaptation to a new motor position, and hence most monocular exotropes have an amblyopia of arrest with normal retinal correspondence. Monocular and alternating exotropes may, at the outset of the disease process, differ only slightly in the degree of blur of the retinal image in one eye as compared with the fellow eye. When the differential blur is significant, the route of a monocular exotrope may be taken rather than an alternating equal visioned exotrope. In constant alternating exotropia, the visual acuity is characteristi cally equal in the two eyes, the hemiretinal suppression becomes a sensory adaptation, and anomalous retinal correspondence is usually present. It is in this type of strabis mus that the deviation becomes of very large magnitude and all the sensory-motor anomalies most profound indeed. The anatomic (motor) factors in the man agement of exotropia are also of extreme importance. Anyone who has operated upon patients with constant alternating exotropia of large degree cannot help but be im pressed by the purely mechanical difficulties in effecting straight eyes by surgery upon the extraocular musculature and the surrounding structures. Most of these, however, are sec ondary anatomic effects consequent to the widely divergent position of the eyes over a period of time. In the management of di vergent ocular deviation both the sensory and anatomic factors require special attention. While it is probably true that the anatomic
646
SURGICAL MANAGEMENT OF EXOTROPIA
machinery is primarily at fault during in fancy, it is the sensory suppression mecha nism that proves to be the more important problem in the management during later in fancy and early visual adulthood. Once the constant alternating, or monocular, divergent stage is reached, the secondary anatomic factors indeed become a large problem in management. Now both the sensory and an atomic factors are considerable, and form the basis for the widespread dissatisfaction with the present methods of treating this latter type of case. In the management of exotropia, the pres ence of a good fusion potential is the sur geon's best assistant, and the lack of this potential, in the form of sensory suppression, is his worst antagonist. This factor is so ger mane to the proper evaluation of surgical management of exotropia that one cannot afford to omit it in assessing the mechanical effects of surgical techniques. Although it is desirable when possible to incorporate pre- and postoperative antisuppression orthoptics as an adjunct to surgery, the surgery alone may do this via overcorrec tion of the exotropia. Unwittingly or un knowingly, ophthalmic surgeons use sur gical instruments as orthoptic instruments by jolting the fusion mechanism through sur gery. Surgical overcorrection of exotropia in variably results in diplopia which may be sufficient to awaken an always dormant normal correspondence fusion and result in greater percentage of cures. Surgical treat ment may influence not only the anatomic factors, but, through surgical overcorrection of the defect, may also materially influence the sensory mechanism. Vertical noncomitancy is a common occur rence in both monocular and alternating exotropia. This is usually due to secondary involvement of the oblique muscles in the divergent eye. A divergent position of an eye favors shortening of both obliques with consequent overaction and contractures. The more constant the deviation, and the greater the magnitude of deviation, the more marked
647
the overactions of the obliques. It is not un common to find an overaction of both agonist and antagonist obliques in the same eye. In alternating exotropia, the oblique overactions, if present, may not be equal in both eyes with a consequent hypertropia. Sym metric bilateral overaction of both super ior oblique muscles is best detected by ex amination of the direct up versus the direct down fields of gaze. The difference in hori zontal components of the deviation may dif fer by as much as 80 prism diopters in these two positions of gaze. SURGERY OF MONOCULAR EXOTROPIA
The treatment is usually for cosmetic pur poses since the exotropic eye is usually amblyopic. It is not unusual, however, to find a functional as well as a good cosmetic result with stable peripheral fusion. One recalls that such patients have a good normal retinal correspondence fusion potential. Monocular surgery is indicated, and is usually re-em phasized by the fact that the patient will not allow surgical attack upon the good eye. Full recession (seven to eight mm.) of the lateral rectus is indicated, combined with substantial resection of the medial rectus (the degree of resection depends upon the magnitude of deviation). Proper isolation of the medial rectus with severing of the intermuscular membranes and check ligaments allows large resection of this muscle to be done without untoward effects upon the palpebral fissure and caruncle position. When, after severance of the horizontal recti, there is still difficulty in mobilizing the globe and rotating it na sally, one may enhance the mobility of the globe by weakening the proper oblique mus cles. An anatomic contracture of one or both obliques may prevent adequate nasal rotation of the globe. When one oblique markedly overacts relative to the other, it alone may be tenotomized. When both obliques over act markedly in the monocular amblyopic exotrope, then both obliques may be tenoto mized fully. It must be emphasized that tenotomy of a superior oblique muscle is an
648
ARTHUR JAMPOLSKY
irreparable procedure and should not be done in a seeing eye without very proper and strict indications. However, in an amblyopic eye which is not visually rehabilitable, tenotomy of one or both obliques is permissible to enhance mobility of the markedly diver gent eye. The forced duction test at the time of surgery as well as ocular rotations preoperatively will dictate this procedure. SURGERY OF CONSTANT ALTERNATING EXOTROPIA
These adult patients usually have an exotropia of very large magnitude and of very long standing. It is not surprising, therefore, that the most profound sensory anomalies are found as well as marked secondary ana tomic effects. The early literature describes placing a stay suture from the eye to the brow or nose in order to "hold" the eye in position. Symmetric, bilateral, and preferably simul taneous bilateral, surgery is indicated. It is well known that simultaneous surgery on both agonist and antagonist enhances the mechanical effect from what might be ex pected by the same surgical procedure on either muscle when done as a sole procedure or at different times. Similarly, simultaneous bilateral surgery enhances the mechanical effect of the surgical re-alignment over what might be expected when monocular surgery is done in separate stages. When the time interval is shortened between the two-stage monocular surgical procedures, the mechani cal effects are enhanced. When the time in terval is shortened to zero (simultaneous bilateral surgery) one succeeds in obtaining large amounts of correction, which is usually indicated in these patients. One should aim at a slight overcorrection of the entire devi ation by operating upon the four horizontal recti at one surgical session. Both lateral recti are recessed fully (seven to eight mm.), one medial rectus is resected, and the other medial rectus is shortened preferably by an O'Conner cinch operation. The latter pro cedure is a "safety valve" and allows regu lation of the postoperative effect within the
first 48 hours postoperatively by removing some of the cinch material. In true alternating exotropia, the oblique overactions are usually (although not al ways) symmetric and are ameliorated sym metrically with surgical re-alignment by at tack upon the four horizontal recti alone. Such symmetric, simultaneous, bilateral surgery profoundly affects the sensory mechanism. It has been my experience that postoperative drift is negligible following such procedures, and that normal retinal cor respondence and the dormant good fusion po tential are allowed to manifest themselves. The attainment of both a functional and a cosmetic result with this procedure is not unusual, and is in contrast to the results achieved by less bold procedures. The empirically determined surgical in dications with respect to time of operation, type of operation, and slight postoperative overcorrection, are all mechanical dictates of the sensorial mechanism, which is of es pecial importance in the management of con stant exotropia. SUMMARY
Constant exotropia is characteristically a disease of visual adults. Its surgical manage ment differs from that in exophoria and in termittent exotropia. The sensory defects in monocular and alternating exotropia are discussed. The motor defects are usually secondary, with frequent involvement of the oblique muscles. The surgery of constant monocular ex otropia is usually cosmetic in purpose and may be confined to monocular surgery. The surgery of constant, alternating ex otropia of large degree should be directed at a symmetric, simultaneous, bilateral surgi cal procedure upon the four horizontal recti muscles. The concept of "surgical orthoptics" is discussed. Secondary divergence (exotropia) is not included in this discussion. 2400 Clay Street (15).
For the purposes of this presentation, exo tropia will be considered as a constant rela tive divergence of the visual axes for any given fixation distance. This is by way of contrast to exophoria and intermittent exo tropia. It is the element of constancy which differentiates the problem under discussion from the latter two instances. Patients with constant exotropia exhibit the most profound sensory- motor anomalies. Constant exotropia is the last stage of a pro gressive disease process. It is of interest to note that one does not see infants with constant exotropia, except in bizarre in stances. Visual infants (under six years of age) may exhibit a constant exotropia only in later years, and as a rule do not develop the con stancy until after the age of six years. The surgical management of constant exotropia, therefore, is primarily concerned with visual adults, who possess less adapt ability of the sensory mechanisms. Since all constant exotropes have passed through the earlier stages of exophoria and intermittent exotropia, it is paradoxical that they all have experienced good binocular fusion, while at the same time have de veloped a most profound sensory suppres sion and secondary motor defects. It will be the purpose of this paper to point out the sensory and motor defects asso ciated with constant monocular and constant alternating exotropia, and, by example, to show the surgical steps directed at affecting both the sensory and motor aspects of the problem. What are the sensory-motor defects in constant exotropia? Hemiretinal regional * From the Department of Surgery (Ophthal mology), Stanford University School of Medicine. Presented at the V I I Congress of the Pan-Pacific Surgical Association, Honolulu, November 14-22, 1957.
suppression is large in extent and deep. Monocular amblyopes characteristically have a "built-in" suppression. That is, it is usual to be able to account for an over-all blur of the retinal image in one eye by a significant amount of anisometropia, a corneal scar, lens opacity, or some similar such phenomenon. With such "ready-made" suppression it is not necessary for the sensory mechanism to make such a marked adaptation to a new motor position, and hence most monocular exotropes have an amblyopia of arrest with normal retinal correspondence. Monocular and alternating exotropes may, at the outset of the disease process, differ only slightly in the degree of blur of the retinal image in one eye as compared with the fellow eye. When the differential blur is significant, the route of a monocular exotrope may be taken rather than an alternating equal visioned exotrope. In constant alternating exotropia, the visual acuity is characteristi cally equal in the two eyes, the hemiretinal suppression becomes a sensory adaptation, and anomalous retinal correspondence is usually present. It is in this type of strabis mus that the deviation becomes of very large magnitude and all the sensory-motor anomalies most profound indeed. The anatomic (motor) factors in the man agement of exotropia are also of extreme importance. Anyone who has operated upon patients with constant alternating exotropia of large degree cannot help but be im pressed by the purely mechanical difficulties in effecting straight eyes by surgery upon the extraocular musculature and the surrounding structures. Most of these, however, are sec ondary anatomic effects consequent to the widely divergent position of the eyes over a period of time. In the management of di vergent ocular deviation both the sensory and anatomic factors require special attention. While it is probably true that the anatomic
646
SURGICAL MANAGEMENT OF EXOTROPIA
machinery is primarily at fault during in fancy, it is the sensory suppression mecha nism that proves to be the more important problem in the management during later in fancy and early visual adulthood. Once the constant alternating, or monocular, divergent stage is reached, the secondary anatomic factors indeed become a large problem in management. Now both the sensory and an atomic factors are considerable, and form the basis for the widespread dissatisfaction with the present methods of treating this latter type of case. In the management of exotropia, the pres ence of a good fusion potential is the sur geon's best assistant, and the lack of this potential, in the form of sensory suppression, is his worst antagonist. This factor is so ger mane to the proper evaluation of surgical management of exotropia that one cannot afford to omit it in assessing the mechanical effects of surgical techniques. Although it is desirable when possible to incorporate pre- and postoperative antisuppression orthoptics as an adjunct to surgery, the surgery alone may do this via overcorrec tion of the exotropia. Unwittingly or un knowingly, ophthalmic surgeons use sur gical instruments as orthoptic instruments by jolting the fusion mechanism through sur gery. Surgical overcorrection of exotropia in variably results in diplopia which may be sufficient to awaken an always dormant normal correspondence fusion and result in greater percentage of cures. Surgical treat ment may influence not only the anatomic factors, but, through surgical overcorrection of the defect, may also materially influence the sensory mechanism. Vertical noncomitancy is a common occur rence in both monocular and alternating exotropia. This is usually due to secondary involvement of the oblique muscles in the divergent eye. A divergent position of an eye favors shortening of both obliques with consequent overaction and contractures. The more constant the deviation, and the greater the magnitude of deviation, the more marked
647
the overactions of the obliques. It is not un common to find an overaction of both agonist and antagonist obliques in the same eye. In alternating exotropia, the oblique overactions, if present, may not be equal in both eyes with a consequent hypertropia. Sym metric bilateral overaction of both super ior oblique muscles is best detected by ex amination of the direct up versus the direct down fields of gaze. The difference in hori zontal components of the deviation may dif fer by as much as 80 prism diopters in these two positions of gaze. SURGERY OF MONOCULAR EXOTROPIA
The treatment is usually for cosmetic pur poses since the exotropic eye is usually amblyopic. It is not unusual, however, to find a functional as well as a good cosmetic result with stable peripheral fusion. One recalls that such patients have a good normal retinal correspondence fusion potential. Monocular surgery is indicated, and is usually re-em phasized by the fact that the patient will not allow surgical attack upon the good eye. Full recession (seven to eight mm.) of the lateral rectus is indicated, combined with substantial resection of the medial rectus (the degree of resection depends upon the magnitude of deviation). Proper isolation of the medial rectus with severing of the intermuscular membranes and check ligaments allows large resection of this muscle to be done without untoward effects upon the palpebral fissure and caruncle position. When, after severance of the horizontal recti, there is still difficulty in mobilizing the globe and rotating it na sally, one may enhance the mobility of the globe by weakening the proper oblique mus cles. An anatomic contracture of one or both obliques may prevent adequate nasal rotation of the globe. When one oblique markedly overacts relative to the other, it alone may be tenotomized. When both obliques over act markedly in the monocular amblyopic exotrope, then both obliques may be tenoto mized fully. It must be emphasized that tenotomy of a superior oblique muscle is an
648
ARTHUR JAMPOLSKY
irreparable procedure and should not be done in a seeing eye without very proper and strict indications. However, in an amblyopic eye which is not visually rehabilitable, tenotomy of one or both obliques is permissible to enhance mobility of the markedly diver gent eye. The forced duction test at the time of surgery as well as ocular rotations preoperatively will dictate this procedure. SURGERY OF CONSTANT ALTERNATING EXOTROPIA
These adult patients usually have an exotropia of very large magnitude and of very long standing. It is not surprising, therefore, that the most profound sensory anomalies are found as well as marked secondary ana tomic effects. The early literature describes placing a stay suture from the eye to the brow or nose in order to "hold" the eye in position. Symmetric, bilateral, and preferably simul taneous bilateral, surgery is indicated. It is well known that simultaneous surgery on both agonist and antagonist enhances the mechanical effect from what might be ex pected by the same surgical procedure on either muscle when done as a sole procedure or at different times. Similarly, simultaneous bilateral surgery enhances the mechanical effect of the surgical re-alignment over what might be expected when monocular surgery is done in separate stages. When the time interval is shortened between the two-stage monocular surgical procedures, the mechani cal effects are enhanced. When the time in terval is shortened to zero (simultaneous bilateral surgery) one succeeds in obtaining large amounts of correction, which is usually indicated in these patients. One should aim at a slight overcorrection of the entire devi ation by operating upon the four horizontal recti at one surgical session. Both lateral recti are recessed fully (seven to eight mm.), one medial rectus is resected, and the other medial rectus is shortened preferably by an O'Conner cinch operation. The latter pro cedure is a "safety valve" and allows regu lation of the postoperative effect within the
first 48 hours postoperatively by removing some of the cinch material. In true alternating exotropia, the oblique overactions are usually (although not al ways) symmetric and are ameliorated sym metrically with surgical re-alignment by at tack upon the four horizontal recti alone. Such symmetric, simultaneous, bilateral surgery profoundly affects the sensory mechanism. It has been my experience that postoperative drift is negligible following such procedures, and that normal retinal cor respondence and the dormant good fusion po tential are allowed to manifest themselves. The attainment of both a functional and a cosmetic result with this procedure is not unusual, and is in contrast to the results achieved by less bold procedures. The empirically determined surgical in dications with respect to time of operation, type of operation, and slight postoperative overcorrection, are all mechanical dictates of the sensorial mechanism, which is of es pecial importance in the management of con stant exotropia. SUMMARY
Constant exotropia is characteristically a disease of visual adults. Its surgical manage ment differs from that in exophoria and in termittent exotropia. The sensory defects in monocular and alternating exotropia are discussed. The motor defects are usually secondary, with frequent involvement of the oblique muscles. The surgery of constant monocular ex otropia is usually cosmetic in purpose and may be confined to monocular surgery. The surgery of constant, alternating ex otropia of large degree should be directed at a symmetric, simultaneous, bilateral surgi cal procedure upon the four horizontal recti muscles. The concept of "surgical orthoptics" is discussed. Secondary divergence (exotropia) is not included in this discussion. 2400 Clay Street (15).