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Clinical rationale for manifest congenital nystagmus surgery
Philip Knapp Lecture Clinical Rationale for Manifest Congenital Nystagmus Surgery Annette Spielmann, MD Although electronystagmography is most useful, especially in furthering our knowledge of nystagmus, simple clinical study is the first step to any understanding of nystagmus. Ophthalmologists should be aware that they may understand a good deal about nystagmus merely by studying visual acuity in their surgery. Testing visual acuity at distance with both eyes open will lead to the qualitative and quantitative diagnosis of compensatory abnormal head postures. Testing at distance with 1 eye covered will help to distinguish between the concordant head turn, one eye fixing in abduction and the other fixing in adduction (ABD + ADD) as is seen in manifest congenital nystagmus, and the discordant head turn in which each eye fixes in adduction (ADD + ADD), as is seen in manifest latent nystagmus, for which surgery is totally different. Pseudolatent nystagmus found in congenital nystagmus with exophoria can be differentiated from latent nystagmus. This illustrates de visu (with the naked eye) the “beauty” of the movement of blocking fusional convergence and the nature of the involved mechanisms with artificial divergence surgery. Testing at near will bring out the existence of blocking convergence. Depending on the results, the clinical rationale for surgery is thus made clear: horizontal, vertical, rotatory Kestenbaum-like surgery should be used in cases of abnormal head posture, whereas artificial divergence surgery is our most satisfactory armamentarium in cases of blocking convergence. (J AAPOS 2000;4:67-74)
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aluable papers concerning nystagmus surgery and electronystagmography have been presented at meetings of the American Association for Pediatric Ophthalmology and Strabismus, including a Costenbader lecture.1 Specific suggestions for the ophthalmologist regarding nystagmus are outlined in this article. I should like to stress the usefulness of a very simple clinical approach to patients with nystagmus. Special attention is given to blocking convergence and, in particular, to fusional blocking convergence, which may be evaluated de visu (with the naked eye) in patients with pseudolatent congenital nystagmus. Nystagmus means “rhythmical involuntary to-and-fro movement of the eyes.” Congenital ocular nystagmus is caused by the inability to keep the target on the fovea.2 Congenital manifest nystagmus, as defined by Von Noorden,3 is the consequence of fixation misdevelopment. This differentiates it from manifest/latent nystagmus, which is not addressed in this paper. Thus, there is no congenital nystagmus in the absence of fixation. It is triggered by fixation and is aggravated by any effort of fixation; this is the basis for the clinical examination. Presented as the Philip Knapp Lecture at the 25th Annual Meeting of the American Association for Pediatric Ophthalmology and Strabismus, Toronto, Ontario, April 17, 1999. Submitted April 17, 1999. Revision accepted August 10, 1999. Reprint requests: Annette Spielmann, MD, 11 rue de la Ravinelle, Nancy, France. Copyright © 2000 by the American Association for Pediatric Ophthalmology and Strabismus. 1091-8531/2000 $12.00 + 0 75/1/103433 doi:10.1067/mpa.2000.103433
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Congenital nystagmus may be stabilized by supplementary innervations of version and/or of vergence. These are referred to as compensatory mechanisms; these constitute the main basis for surgery. Taken together these 2 notions supply the clinical rationale underlying congenital nystagmus surgery.
CLINICAL BASIS FOR SURGERY Surgical Principles Surgery to damp nystagmus is based on 2 principles referred to by Crone4 as immobilization and relocation of the eyes. Immobilization procedures were the first to be used historically. In 1933, Blatt5 performed tenotomies of the 4 horizontal rectus muscles. Muhlendyck6 proposed a fadenoperation on the 4 rectus muscles in 1978. Recently, E. Limon de Brown7 popularized the retro-equatorial recessions of the 2 horizontal muscles of each eye as initially proposed by Bietti and Bagolini in 1960.8-11 These procedures all aim to lessen muscle efficiency and to reduce nystagmus intensity. However, there are some unexplained issues regarding the actual nature of the mechanisms involved. Their efficiency is unpredictable. In my opinion, they represent “desperate measures,” which are indicated only in the absence of compensatory mechanisms. Diagnosis of these compensatory mechanisms is straightforward. Only relocation procedures are addressed herein. Relocation procedures were first advocated by Kestenbaum2 and Anderson12 in patients with compensatory head turns. These procedures aim to shift both eyes from an eccentered
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FIG 1. Influence of the effort to see on abnormal head postures. A, This head position corresponds vision testing on a 20/60 E-test optotype, B, to a 20/80 optotype, and C, to a 20/200 optotype. It can be seen that the head turn increases with the effort to see and that head tilt progressively appears. The amount of surgery should depend on the degree of of abnormal head posture depicted in A.
position of gaze where nystagmus is damped (null zone) into the primary position. This type of surgery has been extended to more complex abnormal head postures and to blocking convergence as advocated by Adelstein and Cüppers.13 Relocation procedures are recognized as efficient. They are indicated in cases of compensatory mechanisms.
of surgery required. It is frequently suggested that surgical realignment of the eyes when treating nystagmus requires a greater amount of surgery than is performed when treating strabismus. This is not true. In fact, the amount of surgery needed is identical if proper evaluation of the gaze eccentration has been determined, as suggested above.
Manifest Congenital Nystagmus and Compensatory Mechanisms
Testing Visual Acuity at Distance With Both Eyes Open
Congenital nystagmus is manifest and present during binocular fixation. As described by Dell’Osso and Daroff,14 it may be pendular, or it may jerk with an increasing velocity slow phase. The compensatory mechanisms are (1) innervation of version, which is horizontal version leading to horizontally eccentric null zone and head turn, vertical version leading to vertically eccentric null zone and to chin elevation or depression, and cycloversion with head tilt (without eccentric gaze in the pure forms) and (2) innervation of vergence, which invariably involves blocking convergence. Binocular vision is not a compensatory mechanism and may aggravate nystagmus. Strabismus can be an additional problem. Manifest congenital nystagmus should be distinguished from manifest/latent nystagmus for which the compensatory mechanisms include fixation in adduction and bilateral retinal stimulation. Consequently, surgery for these 2 entities is different.15,16 Immediate diagnosis is difficult when latent nystagmus is manifest. However, as will be seen, this can be sorted out by clinical examination.
DIAGNOSIS Planning Surgery by Means of Visual Acuity Testing Planning surgery requires correct diagnosis of compensatory mechanisms. If compensatory mechanisms are present, quantification of surgery must be based on appropriate effort of fixation: the greatest possible effort should be asked of the patient by testing visual acuity at its highest level. As shown in Figure 1, the initial head turn increases with the effort to see, and a head tilt progressively appears. This final abnormal head position (Figure 1, A) indicated the degree
Visual acuity should first be tested at distance with both eyes open to determine the existence and the type of abnormal head postures adopted by the patient. These are under the influence of the dominant eye. I usually evaluate them with a torticollimeter. (I measure the head turns with a “highly sophisticated” instrument: a compass). To supply data for this presentation I undertook a study of patients with nystagmus whom I treated. During the first 4 months of 1998, I operated on 67 patients with manifest nystagmus; 47 patients had manifest congenital nystagmus. I studied their records and refer repeatedly to the results of that study throughout this article. When tested in the manner described above, the patients with manifest congenital nystagmus (n = 47) in that series adopted one of the following 7 positions: 1. No abnormal head posture (3 patients [6%]). In these patients the head and eyes are the same as in healthy individuals. This indicates an absence of compensatory mechanisms. These 3 patients underwent a large recession of the 4 horizontal rectus muscles. 2. A unidirectional head turn (12 patients [26%]). The head turn was associated with blocking convergence in 5 other cases. Head turns are usually referred to as horizontal torticollis in Europe. 3. An alternating or bidirectional head turn (6 patients [13%]). Tests should be repeated several times and over a long enough period of time to detect cases of this pattern that I described in 1983.17 I labeled this disorder a double or bidirectional head turn. It was subsequently more appropriately renamed alternating head turn by Von Noorden.3 These head turns may be a variant of, but are not, true periodic alternant nys-
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FIG 2. Concordant head turn (one eye fixes in adduction and the other in abduction) with congenital nystagmus associated with blocking convergence (top row of photographs). The largest amount of prism-induced convergence that damps nystagmus without creating diplopia is determined with the Berens prism bar (A). The patient tolerates 40 PD of base-out prism without diplopia. B, A 30 base-out prism is affixed to the right lens. The test is continued with the Berens bar on the left eye. Diplopia occurs with 30 base-out prism. C, Press-on prisms of this amount are affixed to the glasses. Finally, the nystagmus is blocked at distance by with PD base-out, and no diplopia is induced. A 9-mm (from the insertion) adjustable suture bilateral recession may be planned.
tagmus. Inversion of nystagmus occurs in a random rather than a cyclic pattern as was characteristic of the cases described by Gradstein et al18 and by Robb.19 Two steady null zones, one to the left and one to the right, can be observed. Occasionally, the second null zone may be adopted. It is necessary to determine whether the second null zone is present. Sometimes one null zone is used at distance, and the other is used at near. The patient may purposely reverse the head turn when he or she is tired. The “null zone” may be the ambiversive null zone described by Dietele20 (eg, the direction of nystagmus reverses beyond this null zone). In the video presentation shown during the lecture the second head turn was actually induced by asking the patient to look beyond this null zone to the right and then by occluding the right visual field. Bidirectional head turns are relatively frequent if looked for (6 patients [13%] in my series). Fortunately, for the treatment of most of these patients, there is an associated blocking convergence permitting artificial divergence surgery. 4. A blocking convergence (5 patients [10%]). 5. A vertical abnormal head posture (7 patients [15%]). This is referred to as vertical torticollis in Europe and consists of a chin elevation or chin depression. 6. A pure head tilt (1 patient [2%]). In cases of innervational blocking head tilt, no cyclotorsion is detected by fundus examination. 7. A mixed head position (13 patients [28%]). This type
is the most frequent if the patients are properly evaluated (Figure 1). At this point we know whether there is an abnormal head posture, but it is still necessary to determine the exact influence of monocular occlusion on the head turn and on the nystagmus. Visual Acuity Testing, One Eye Covered This part of the examination is mandatory. It helps to differentiate congenital nystagmus from latent nystagmus and to uncover the possible presence of pseudolatent nystagmus and de visu the presence of blocking fusional convergence. Influence of monocular occlusion on the head turn. Straightforward diagnosis of the type of nystagmus is achieved by occlusion of 1 eye, which induces monocular fixation. In manifest congenital nystagmus the head turn is concordant: one eye fixates in abduction, and the other fixates in adduction (ABD + ADD). In other words, the same direction of head turn is adopted when either eye takes up fixation as well as during binocular fixation (Figure 2).15 The surgical shift of the eyes should also be concordant (ie, in the same direction for both eyes). In manifest latent nystagmus the head turn is discordant: each eye fixes in adduction (ADD + ADD). (I find the term alternating confusing.) The head turn and the nystagmus direction reverse when fixation shifts from one eye to the other. The surgical shift of the eyes should also be discordant (ie, an opposite direction for each eye). The discordant head turn in Figure 3 (each eye fixing in adduction [ADD + ADD]) should have been distinguished from the
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FIG 3. Typical discordant head turn in manifest latent nystagmus characterized by fixation in adduction of each eye (A-C). The head turn and nystagmus direction reverse when fixation shifts from one eye to the other. During fixation with both eyes open (B), nystagmus is absent, and the head turn direction is determined by the left dominant eye. D, Situation after “discordant “ surgery (a 4-mm recession plus a fadenoperation at 13 mm on both medial rectus muscles). It should be noted that a fadenoperation is frequently indicated in patients with manifest latent nystagmus but never in patients with blocking convergence.
FIG 4. Pseudolatent congenital nystagmus. A, The eyes are straight, and nystagmus is absent (corresponds to electronystagmogram 1’). B, Occlusion of the right eye simultaneously triggers divergence of the covered eye and pendular nystagmus (corresponds to electronystagmogram 2’). C, In the fixation-free position observed under bilateral occluders (through which the eyes can be seen but through which the patient only has blurred vision) is an exoposition; the exodeviation is not innervational. In this case of exophoria, congenital nystagmus is triggered by occlusion, which disrupts fusional blocking convergence.
concordant head turn (one eye fixating in abduction, the other in adduction [ABD + ADD]) in Figure 2. The influence of occlusion on nystagmus intensity. Latent nystagmus is defined as a nystagmus triggered by occlusion. Pseudolatent congenital nystagmus is also an occlusion-triggered nystagmus but is of the congenital type with respect to waveform. This is why I named it pseudolatent congenital nystagmus in 1991.21 It is present in patients with congenital nystagmus who have exophoria (Figure 4). There is no nystagmus in the fusing state: nystagmus and divergence appear with occlusion of 1 eye, which disrupts fusion. The fusional convergence that controls the exodeviation at distance damps the nystagmus. When the occluder is removed leaving both eyes uncovered, an impressive movement of convergence reestablishing orthophoria and suppressing the nystagmus can be observed. Nystagmus also reappears with base-in prisms, which suppress the convergence effort. The exodeviation may be primary or secondary to artificial divergence surgery.22 It is not an innervational deviation because a fixation-free exoposition is observed behind 2 translucent occluders. Proper diagnosis is mandatory because surgery to correct the exotropia is contraindicated (or at least, should aim to undercorrect the exotropia). Kommerell et al,23 who described patients with
exophoria and exotropia in whom nystagmus was present in the tropic state but not in the phoric state, drew the same conclusion. Videotape presentation of the movement of blocking fusional convergence can be shown to patients during office consultation. This is useful in explaining to patients (who cannot see their own nystagmus) that it is better, functionally and cosmetically, to experience an occasional exotropia than permanent nystagmus. These patients are a most striking example of what blocking fusional convergence is. They also give us an idea of how artificial divergence surgery works. Visual Acuity Testing at Near and Prism Adaptation Test Visual acuity is always tested at 30 cm, but the distance at which blocking convergence occurs should be evaluated. Once the damping of nystagmus at near fixation has been observed, a careful study of fusion should be carried out. Because the aim of surgery is to create an innervation of convergence at distance by recessing the medial rectus muscles, prism adaptation is mandatory (VeronneauTroutman24). As illustrated in Figure 2, prisms determine the largest amount of prism-induced convergence that damps nystagmus without creating diplopia.
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FIG 5. Chin elevation and vertical Kestenbaum-type surgery. Chin elevation ≥40° both monocular and binocular (A-C). D, After surgery, which consited of a 7-mm recession of both inferior rectus muscles plus a 6-mm resection of both superior rectus muscles. Abnormal head posture has been eliminated, and the patient can look through the optical center of the spectacles.
FIG 6. Each closed square denotes the amount of abnormal head posture in degrees in an individual patient before surgery, and each closed triangle denotes the amount after surgery to correct the abnormal vertical head posture. Top, Chin elevation was ≥30° in all patients. Preoperative mean value was 40.3°; postoperative mean value was 7°(correction = 33.3°). The quantity of surgery had a mean value of 8 mm on each muscle. A rough approximation is that 1 mm of surgery corrects a 4.2° vertical head rotation. Bottom, Chin depression had a mean value of 24.5° before surgery and 2.5° after surgery (mean correction = 20.3°). The quantity of surgery had a mean value of 5.8 mm on each muscle; 1 mm corrects approximatively 3.7° of chin depression.
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FIG 7. Right head tilt with left cycloversion. An opposing right cycloversion may be obtained by creating excyclotorsion of the right eye and incyclotorsion of the left eye. This may be obtained by (1) recess-resect of the oblique muscles28; (2) surgery on the 4 cyclovertical muscles30: recession of the right superior oblique muscle and adjustable suture recession of the right superior rectus muscle (both incyclotortors), and recession of the left inferior oblique muscle and adjustable suture recession of the left inferior rectus muscle (both excyclotortors); (3) slanting of the 4 rectus muscles31: an oblique recession of 7 mm of the superior fibers of the medial rectus muscle, the nasal fibers of the inferior rectus muscle, the inferior fibers of the lateral rectus muscle, and the temporal fibers of the superior rectus muscle creates incyclotorsion. Conjugate slanting of the rectus muscles in the other eye creates excyclotorsion; (4) horizontal transposition of the vertical rectus muscle tendon.32 This transposition may be extended to any rectus muscle, depicted here as also involving horizontal rectus muscles; and (5) horizontal transposition of the vertical rectus muscle tendons.32 This transposition may be extended to any rectus muscle.
The distribution of the prisms between the 2 eyes must also be evaluated. A head turn reversal may occur when unilateral prisms are used. This is a sign of an underlying alternating headturn. At this point we know (1) the patient’s visual acuity in different conditions of fixation and (2) the nystagmus behavior in the same conditions of fixation. We have established whether we are dealing with congenital nystagmus or with manifest/latent nystagmus, what the compensatory mechanisms are, if any, and what their intensity is. We are ready to plan surgery. This surgery may be Kestenbaum-like surgery or artificial divergence surgery.
SURGERY25 Blocking Versions: The Kestenbaum-Anderson–Like Procedures Head turns require a horizontal concordant shift of the eyes. This is frequently referred to as a horizontal Kestenbaum or a horizontal Kestenbaum-Anderson procedure, in reference to the 2 ophthalmologists who proposed this type of surgery.2,12 It is common knowledge that in a patient with a concordant left head turn (the left eye fixing in adduction, the
right in abduction), if the eyes are steady 30° to the right, they must be surgically relocated, that is, shifted 30° to the left. An Anderson-like procedure for such a patient would consist of a supralarge recession of the right lateral rectus and left medial rectus muscles. This procedure is currently popular in Europe. A Kestenbaum procedure combines the recession of the Anderson-like procedure with resections of the antagonist muscles. With vertical abnormal head postures, the same rationale may be applied as is used for horizontal head turns. When nystagmus is absent in downward gaze, which induces chin elevation, the eyes should be surgically shifted upward by a similar amount (Figure 5). Adjustable suture surgery on both inferior rectus muscles is advisable. In a study of 82 patients, Spielmann and Spielmann26,27 found that results were satisfactory, as illustrated in Figure 6. No cyclodeviation was induced with surgery, and 1 mm of surgery corrected approximately 4° of chin depression and 3.6° of chin elevation (Figure 6). Head tilts are the consequence of a compensatory cycloversion. A right head tilt corresponds to a blocking innervation of incyclotorsion in the right eye and of excyclotorsion in the left eye (Figure 7). Surgery aims to create an
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FIG 8. Left head turn associated with left head tilt. A, Surgery was a horizontal Kestenbaum (8 mm recess/resect) associated with a downward transposition of the recessed right lateral rectus and left medial rectus muscles. B, Head posture after surgery.
excyclotorsion of the right eye and an incyclotorsion of the left eye. This type of surgery was named Rotatory or Oblique Kestenbaum by Conrad and de Decker28 who suggested rotating both eyes around the sagittal axis using recess-resect procedure on all the oblique muscles. This surgery frequently induces vertical imbalance, even if associated with anteroposition and retroposition of these muscles. Consequently, it has subsequently been modified by de Decker.29 I proposed recessions of the 4 cyclovertical muscles, using adjustable sutures on the rectus muscles, to avoid vertical imbalances.30 I subsequently adopted slanting of the rectus muscle insertions.31 Von Noorden et al32 proposed transposition of the vertical rectus muscles horizontally, which follows the same principle, but it is simpler and more efficient. It may be extended to any horizontal rectus muscle.29 Mixed cases are frequent. They may benefit from surgery that combines all of all the previously described procedures. For example, a left head turn with a left head tilt may benefit from the combination of a horizontal Kestenbaum with a transposition of the tendons as illustrated in Figure 8. Blocking Convergence and Artificial Divergence Surgery The diagnosis of blocking convergence is extremely simple. The aim of treatment is to create a supplementary convergence effort at distance that should damp the nystagmus. Obviously this effort, which is fusional and tonic in nature, is only possible in patients with good fusion. That is why a careful study of fusion must be carried out, as demonstrated in Figure 2. Artificial divergence surgery is the name given to this procedure by Cüppers and Adelstein.13 I perform bilateral medial rectus muscle recessions ranging from 5 to 13 mm depending on the predetermined amount of the prism as described above. I welcome the opportunity to use adjustable suture surgery as soon as a patient is old enough to permit that technique. Whenever I use adjustable sutures with artificial divergence surgery, I recess each medial rectus muscle 10 to 13 mm from the insertion. In young patients, the amount of recession depends on the amount of fusion found. I recommend 5 mm recesssions if
fusion is 30 PD/40 PD, 7 mm if fusion is 50 PD/60 PD, and 8 mm if fusion exceeds 60 PD. I do not favor unilateral procedures, which run the risk of creating inversion of a preexistent head turn, as may be seen with the use of unilateral prisms. In my opinion the fadenoperation, which increases the convergence effort mainly at near, is not indicated in treating these patients. Blocking convergence is frequently associated with a head turn. In such cases, artificial divergence surgery is preferable to Kestenbaum-like surgery, except in very young children who are prone to have a consecutive exotropia with artificial divergence operation, as seen in the retrospective study described below. In a retrospective study of 120 cases that I presented in 1992, I obtained orthophoria in 93 patients (77.5%).33 The results was slightly unsatisfactory in 23 of these 93 patients, because they still had a slight nystagmus in primary gaze with a small residual head turn. Eighteen patients ended up with exophoria, giving rise to pseudolatent nystagmus (no surgery was required). Only 9 patients were exotropic. These were mainly children with hypermetropia who were younger than 8 years (6 patients underwent surgery to undercorrect the divergence). The exotropia invariably occurred during the first year after surgery. Surprising as it sounds, we may consider that fusional convergence gives way rapidly to tonic convergence in more than 77% of the cases. A satisfactory postoperative residual fusional amplitude helps ensure the stability of the results. Four types of blocking convergence exist: fusional blocking convergence, blocking convergence of the near vision complex, prism-induced blocking convergence, and surgery-induced blocking convergence. Artificial divergence surgery is probably the most efficient procedure I know of for treating nystagmus. It is the only recourse in patients with alternating head turns with 2 null zones if blocking convergence is present. Age and Results Patients may benefit from surgery at any age. There is no need for early surgery in children except when they have a large torticollis and/or when deprivation nystagmus amblyopia might possibly develop. For example, this
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might occur in patients with ametropia, in particular if there is a large amount of astigmatism. In this situation a large abnormal head posture may prevent the patient from correctly looking through the optical center of the spectacles (Figure 5). Children with abnormal head postures less than or equal to 20° really do not require surgery. There may be an increase in the need for surgery after age 40 years when the patient’s neck is no longer supple and presbyopia has begun. An exception to this is if head flexion is present. It should always be treated because it causes a substantial handicap for work at near. In most patients, surgery does not improve visual acuity per se; it does not improve beyond that experienced before surgery in the compensatory abnormal head posture at distance or at near viewing. However, surgery increases the availability of this higher visual acuity and enlarges the visual field through transferring this acuity onto the primary position. “Vision” can be said to have been improved. Finally, the improvement is not only visual and cosmetic, but also social, through the decrease of the severe abnormal head postures and damping nystagmus in everyday situations.
CONCLUSION Nystagmus should not be a mystery for ophthalmologists. Electronystagmography is certainly most useful, especially in furthering our knowledge of nystagmus. However simple clinical study is the first step to any understanding of nystagmus. Ophthalmologists should be aware that they may understand a good deal about nystagmus simply by studying vision and visual acuity, something which they do in their everyday practice. Finally, I would like to stress the value of blocking convergence. It is a very powerful blocking mechanism that is easily detected during office examination. Patients with exophoria with pseudolatent congenital nystagmus are certainly a fascinating illustration of what fusional blocking convergence is, and the best argument in favor of artificial divergence surgery. References 1. Reinecke RD. Idiopathic infantile nystagmus: diagnosis and treatment. J Ped Ophthalmol Strabismus 1997;1:67-82. 2. Kestenbaum A. Clinical methods of neuro-ophthalmologic examination. New York: Grune & Stratton; 1946. 3. Noorden Von GK. Binocular vision and ocular motility: theory and management of strabismus. 5th ed. St Louis: Mosby; 1996. 4. Crone RA. The operative treatment of nystagmus. Ophthalmologica (Basel) 1971;163:15-20. 5. Blatt N. Ist guenstige Beinflussung oder gar Heilung des Nystagmus mittels lokaler cjirurgischer Intervention moeglich. Acta IV Cong Ophth Hisp 1933;4:437. 6. Muhlendyck H. The fadenoperation in the treatment of congenital nystagmus. In: Reinecke RD, editor. Strabismus. New York: Grune & Stratton; 1978. p. 235-48. 7. Limon de Brown E, Bernardelli J Corvera. Metodo debilitante para el tratamiento del nystagmus. Rev Mex Oftalm 1989;63:65-7. 8. Bietti CB, Bagolini B. Traitement médico-chirurgical du Nystagmus. Année Thérapeutique et Clinique en Ophtalmologie 1960;9:269-96.
9. Spielmann A. Bourron-Madignier M. Recul des 4 muscles droits dans les nystagmus congénitaux. Bull Soc Fr Ophtalmol 1993;11:991-6. 10. Noorden Von GK, Sprunger DT. Large rectus muscle recessions of the treatment of congenital nystagmus. Arch Ophthalmol 1991;109:221-4. 11. Helveston EM, Ellis FD, Plager DA. Large recession of the horizontal recti for treatment of nystagmus. Ophthalmology 1991;98:1302-5. 12. Anderson J. Causes and treatment of congenital eccentric nystagmus. Br J Ophthalmol 1953;37:267-681. 13. Cüppers C, Adelstein FE. Probleme der operativen. Therapie des okülaren Nystagmus. Klin Mbl Augenheilk 1971;159:145-57. 14. Dell’Osso LF, Daroff RB. Congenital nystagmus waveforms and foveation strategy. Doc Ophthalmol 1975;39-1:155-82. 15. Spielmann A. Nystagmus congenital essentiel et nystagmus congénital manifeste/latent. J Fr Orthoptique 1986;18:21-35. 16. Spielmann A. Les différents torticolis du patient nystagmique. Symposium sur les Torticolis d’origine oculaire. Bull Soc Belge Ophtalmol 1987;221-222:121. 17. Spielmann A. The various elements of torticollis in nystagmus. In: Ravault AP, Lenk M, editors. Transactions of the 5th Inter. Orthoptic Congress. Lyon, France: Lips; 1984. p. 359-64. 18. Gradstein L, Reinecke RD, Wizov SS, Goldstein HP. Congential periodic alternating nystagmus. Diagnosis and management. Ophthalmology 1997;104-6:918-29. 19. Robb RM. Periodic alteration of null point in congenital nystagmus. Arch Ophthalmol 1972;87:169-73. 20. Dieterle P. La régulation proprioceptive du nystagmus congénital. Clin Univ Ophthalmol 1957;1:429-43. 21. Spielmann A, Spielmann AC. Pseudo-latent nystagmus: congenital nystagmus with exophoria. 20th E.S.A. Congress, Bruxelles, May. In: Kaufmann, H, editor. Transactions of the 20th Congress of E.S.A. Gahmig Druck, Giessen, 1992. p. 77-82. 22. Spielmann A, Dahan A. Double torticollis and surgical artificial divergence in nystagmus. In: Nemet P, Weiss JP. Acta strabologica. CERES, Paris. 1985:187-192. 23. Kommerell G, Gusek G, Gille SU. Kongenitaler Nystagmus und intermittierende Exophoria. Klin Mbl Augenheilk 1992;200:210-2. 24. Veronneau-Troutman S. Prisms in the medical and surgical management of strabismus. St Louis: Mosby Co; 1994. 25. Spielmann A. Surgery to damp nystagmus. In: Spiritus M, editor. Transactions of the 22nd Meeting of European Strabismological Association. Buren, Belgique: Aeolus Press; 1996. p. 286-93. 26. Spielmann AC, Spielmann A. Déséquilibre alphabétiques et recul des muscles droits inférieurs pour déflexion de la tête dans les nystagmus congénitaux. Acta Estrabologica 1995;23:113-8. 27. Spielmann AC, Spielmann A. Bilateral vertical recti recession for vertical abnormal head posture in congenital nystagmus: do they create alphabetic desequilibrium? In: Spiritus M, editor. Transactions of the 22nd Meeting of European Strabismological Association. Buren, Belgique: Aeolus Press; 1996. p. 124-9. 28. Conrad HG, de Decker W. “Rotatorischer Kestenbaum”— Umlagerungschirugie bei Kopfszwangshaltung sur Schulter. Klin Mbl Augenheilk 1978;173:681-90. 29. de Decker W. Kestenbaum transposition in nystagmus therapy. Transposition in horizontal and torsional plane. Bull Soc Belge Ophtalmol 1987;221-222:107-120. 30. Spielmann A. Surgical treatment of nystagmus. J Metabol Ophthalmol 1978;2:157-63. 31. Spielmann A. The “Oblique Kestenbaum” procedure revisited (sloped recessions of the recti). In: Lenk-Schäfer M, editor. Orthoptic horizons. Transactions of the Sixth International Orthoptic Congress, Harrogate, England. 1987. p. 433-7. 32. Noorden Von GK, Jenkis RH, Rosenbaum AL. Horizontal transposition of the vertical rectus muscles for treatment of ocular torticollis. J Ped Ophthalmol Strabismus 1993;30:8-14. 33. Spielmann A. La mise en divergence artificielle dans les nystagmus congénitaux. A propos de 120 cas. Bull Soc Fr Ophtalmol 1993;6/7:571-8.
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aluable papers concerning nystagmus surgery and electronystagmography have been presented at meetings of the American Association for Pediatric Ophthalmology and Strabismus, including a Costenbader lecture.1 Specific suggestions for the ophthalmologist regarding nystagmus are outlined in this article. I should like to stress the usefulness of a very simple clinical approach to patients with nystagmus. Special attention is given to blocking convergence and, in particular, to fusional blocking convergence, which may be evaluated de visu (with the naked eye) in patients with pseudolatent congenital nystagmus. Nystagmus means “rhythmical involuntary to-and-fro movement of the eyes.” Congenital ocular nystagmus is caused by the inability to keep the target on the fovea.2 Congenital manifest nystagmus, as defined by Von Noorden,3 is the consequence of fixation misdevelopment. This differentiates it from manifest/latent nystagmus, which is not addressed in this paper. Thus, there is no congenital nystagmus in the absence of fixation. It is triggered by fixation and is aggravated by any effort of fixation; this is the basis for the clinical examination. Presented as the Philip Knapp Lecture at the 25th Annual Meeting of the American Association for Pediatric Ophthalmology and Strabismus, Toronto, Ontario, April 17, 1999. Submitted April 17, 1999. Revision accepted August 10, 1999. Reprint requests: Annette Spielmann, MD, 11 rue de la Ravinelle, Nancy, France. Copyright © 2000 by the American Association for Pediatric Ophthalmology and Strabismus. 1091-8531/2000 $12.00 + 0 75/1/103433 doi:10.1067/mpa.2000.103433
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Congenital nystagmus may be stabilized by supplementary innervations of version and/or of vergence. These are referred to as compensatory mechanisms; these constitute the main basis for surgery. Taken together these 2 notions supply the clinical rationale underlying congenital nystagmus surgery.
CLINICAL BASIS FOR SURGERY Surgical Principles Surgery to damp nystagmus is based on 2 principles referred to by Crone4 as immobilization and relocation of the eyes. Immobilization procedures were the first to be used historically. In 1933, Blatt5 performed tenotomies of the 4 horizontal rectus muscles. Muhlendyck6 proposed a fadenoperation on the 4 rectus muscles in 1978. Recently, E. Limon de Brown7 popularized the retro-equatorial recessions of the 2 horizontal muscles of each eye as initially proposed by Bietti and Bagolini in 1960.8-11 These procedures all aim to lessen muscle efficiency and to reduce nystagmus intensity. However, there are some unexplained issues regarding the actual nature of the mechanisms involved. Their efficiency is unpredictable. In my opinion, they represent “desperate measures,” which are indicated only in the absence of compensatory mechanisms. Diagnosis of these compensatory mechanisms is straightforward. Only relocation procedures are addressed herein. Relocation procedures were first advocated by Kestenbaum2 and Anderson12 in patients with compensatory head turns. These procedures aim to shift both eyes from an eccentered
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FIG 1. Influence of the effort to see on abnormal head postures. A, This head position corresponds vision testing on a 20/60 E-test optotype, B, to a 20/80 optotype, and C, to a 20/200 optotype. It can be seen that the head turn increases with the effort to see and that head tilt progressively appears. The amount of surgery should depend on the degree of of abnormal head posture depicted in A.
position of gaze where nystagmus is damped (null zone) into the primary position. This type of surgery has been extended to more complex abnormal head postures and to blocking convergence as advocated by Adelstein and Cüppers.13 Relocation procedures are recognized as efficient. They are indicated in cases of compensatory mechanisms.
of surgery required. It is frequently suggested that surgical realignment of the eyes when treating nystagmus requires a greater amount of surgery than is performed when treating strabismus. This is not true. In fact, the amount of surgery needed is identical if proper evaluation of the gaze eccentration has been determined, as suggested above.
Manifest Congenital Nystagmus and Compensatory Mechanisms
Testing Visual Acuity at Distance With Both Eyes Open
Congenital nystagmus is manifest and present during binocular fixation. As described by Dell’Osso and Daroff,14 it may be pendular, or it may jerk with an increasing velocity slow phase. The compensatory mechanisms are (1) innervation of version, which is horizontal version leading to horizontally eccentric null zone and head turn, vertical version leading to vertically eccentric null zone and to chin elevation or depression, and cycloversion with head tilt (without eccentric gaze in the pure forms) and (2) innervation of vergence, which invariably involves blocking convergence. Binocular vision is not a compensatory mechanism and may aggravate nystagmus. Strabismus can be an additional problem. Manifest congenital nystagmus should be distinguished from manifest/latent nystagmus for which the compensatory mechanisms include fixation in adduction and bilateral retinal stimulation. Consequently, surgery for these 2 entities is different.15,16 Immediate diagnosis is difficult when latent nystagmus is manifest. However, as will be seen, this can be sorted out by clinical examination.
DIAGNOSIS Planning Surgery by Means of Visual Acuity Testing Planning surgery requires correct diagnosis of compensatory mechanisms. If compensatory mechanisms are present, quantification of surgery must be based on appropriate effort of fixation: the greatest possible effort should be asked of the patient by testing visual acuity at its highest level. As shown in Figure 1, the initial head turn increases with the effort to see, and a head tilt progressively appears. This final abnormal head position (Figure 1, A) indicated the degree
Visual acuity should first be tested at distance with both eyes open to determine the existence and the type of abnormal head postures adopted by the patient. These are under the influence of the dominant eye. I usually evaluate them with a torticollimeter. (I measure the head turns with a “highly sophisticated” instrument: a compass). To supply data for this presentation I undertook a study of patients with nystagmus whom I treated. During the first 4 months of 1998, I operated on 67 patients with manifest nystagmus; 47 patients had manifest congenital nystagmus. I studied their records and refer repeatedly to the results of that study throughout this article. When tested in the manner described above, the patients with manifest congenital nystagmus (n = 47) in that series adopted one of the following 7 positions: 1. No abnormal head posture (3 patients [6%]). In these patients the head and eyes are the same as in healthy individuals. This indicates an absence of compensatory mechanisms. These 3 patients underwent a large recession of the 4 horizontal rectus muscles. 2. A unidirectional head turn (12 patients [26%]). The head turn was associated with blocking convergence in 5 other cases. Head turns are usually referred to as horizontal torticollis in Europe. 3. An alternating or bidirectional head turn (6 patients [13%]). Tests should be repeated several times and over a long enough period of time to detect cases of this pattern that I described in 1983.17 I labeled this disorder a double or bidirectional head turn. It was subsequently more appropriately renamed alternating head turn by Von Noorden.3 These head turns may be a variant of, but are not, true periodic alternant nys-
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FIG 2. Concordant head turn (one eye fixes in adduction and the other in abduction) with congenital nystagmus associated with blocking convergence (top row of photographs). The largest amount of prism-induced convergence that damps nystagmus without creating diplopia is determined with the Berens prism bar (A). The patient tolerates 40 PD of base-out prism without diplopia. B, A 30 base-out prism is affixed to the right lens. The test is continued with the Berens bar on the left eye. Diplopia occurs with 30 base-out prism. C, Press-on prisms of this amount are affixed to the glasses. Finally, the nystagmus is blocked at distance by with PD base-out, and no diplopia is induced. A 9-mm (from the insertion) adjustable suture bilateral recession may be planned.
tagmus. Inversion of nystagmus occurs in a random rather than a cyclic pattern as was characteristic of the cases described by Gradstein et al18 and by Robb.19 Two steady null zones, one to the left and one to the right, can be observed. Occasionally, the second null zone may be adopted. It is necessary to determine whether the second null zone is present. Sometimes one null zone is used at distance, and the other is used at near. The patient may purposely reverse the head turn when he or she is tired. The “null zone” may be the ambiversive null zone described by Dietele20 (eg, the direction of nystagmus reverses beyond this null zone). In the video presentation shown during the lecture the second head turn was actually induced by asking the patient to look beyond this null zone to the right and then by occluding the right visual field. Bidirectional head turns are relatively frequent if looked for (6 patients [13%] in my series). Fortunately, for the treatment of most of these patients, there is an associated blocking convergence permitting artificial divergence surgery. 4. A blocking convergence (5 patients [10%]). 5. A vertical abnormal head posture (7 patients [15%]). This is referred to as vertical torticollis in Europe and consists of a chin elevation or chin depression. 6. A pure head tilt (1 patient [2%]). In cases of innervational blocking head tilt, no cyclotorsion is detected by fundus examination. 7. A mixed head position (13 patients [28%]). This type
is the most frequent if the patients are properly evaluated (Figure 1). At this point we know whether there is an abnormal head posture, but it is still necessary to determine the exact influence of monocular occlusion on the head turn and on the nystagmus. Visual Acuity Testing, One Eye Covered This part of the examination is mandatory. It helps to differentiate congenital nystagmus from latent nystagmus and to uncover the possible presence of pseudolatent nystagmus and de visu the presence of blocking fusional convergence. Influence of monocular occlusion on the head turn. Straightforward diagnosis of the type of nystagmus is achieved by occlusion of 1 eye, which induces monocular fixation. In manifest congenital nystagmus the head turn is concordant: one eye fixates in abduction, and the other fixates in adduction (ABD + ADD). In other words, the same direction of head turn is adopted when either eye takes up fixation as well as during binocular fixation (Figure 2).15 The surgical shift of the eyes should also be concordant (ie, in the same direction for both eyes). In manifest latent nystagmus the head turn is discordant: each eye fixes in adduction (ADD + ADD). (I find the term alternating confusing.) The head turn and the nystagmus direction reverse when fixation shifts from one eye to the other. The surgical shift of the eyes should also be discordant (ie, an opposite direction for each eye). The discordant head turn in Figure 3 (each eye fixing in adduction [ADD + ADD]) should have been distinguished from the
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FIG 3. Typical discordant head turn in manifest latent nystagmus characterized by fixation in adduction of each eye (A-C). The head turn and nystagmus direction reverse when fixation shifts from one eye to the other. During fixation with both eyes open (B), nystagmus is absent, and the head turn direction is determined by the left dominant eye. D, Situation after “discordant “ surgery (a 4-mm recession plus a fadenoperation at 13 mm on both medial rectus muscles). It should be noted that a fadenoperation is frequently indicated in patients with manifest latent nystagmus but never in patients with blocking convergence.
FIG 4. Pseudolatent congenital nystagmus. A, The eyes are straight, and nystagmus is absent (corresponds to electronystagmogram 1’). B, Occlusion of the right eye simultaneously triggers divergence of the covered eye and pendular nystagmus (corresponds to electronystagmogram 2’). C, In the fixation-free position observed under bilateral occluders (through which the eyes can be seen but through which the patient only has blurred vision) is an exoposition; the exodeviation is not innervational. In this case of exophoria, congenital nystagmus is triggered by occlusion, which disrupts fusional blocking convergence.
concordant head turn (one eye fixating in abduction, the other in adduction [ABD + ADD]) in Figure 2. The influence of occlusion on nystagmus intensity. Latent nystagmus is defined as a nystagmus triggered by occlusion. Pseudolatent congenital nystagmus is also an occlusion-triggered nystagmus but is of the congenital type with respect to waveform. This is why I named it pseudolatent congenital nystagmus in 1991.21 It is present in patients with congenital nystagmus who have exophoria (Figure 4). There is no nystagmus in the fusing state: nystagmus and divergence appear with occlusion of 1 eye, which disrupts fusion. The fusional convergence that controls the exodeviation at distance damps the nystagmus. When the occluder is removed leaving both eyes uncovered, an impressive movement of convergence reestablishing orthophoria and suppressing the nystagmus can be observed. Nystagmus also reappears with base-in prisms, which suppress the convergence effort. The exodeviation may be primary or secondary to artificial divergence surgery.22 It is not an innervational deviation because a fixation-free exoposition is observed behind 2 translucent occluders. Proper diagnosis is mandatory because surgery to correct the exotropia is contraindicated (or at least, should aim to undercorrect the exotropia). Kommerell et al,23 who described patients with
exophoria and exotropia in whom nystagmus was present in the tropic state but not in the phoric state, drew the same conclusion. Videotape presentation of the movement of blocking fusional convergence can be shown to patients during office consultation. This is useful in explaining to patients (who cannot see their own nystagmus) that it is better, functionally and cosmetically, to experience an occasional exotropia than permanent nystagmus. These patients are a most striking example of what blocking fusional convergence is. They also give us an idea of how artificial divergence surgery works. Visual Acuity Testing at Near and Prism Adaptation Test Visual acuity is always tested at 30 cm, but the distance at which blocking convergence occurs should be evaluated. Once the damping of nystagmus at near fixation has been observed, a careful study of fusion should be carried out. Because the aim of surgery is to create an innervation of convergence at distance by recessing the medial rectus muscles, prism adaptation is mandatory (VeronneauTroutman24). As illustrated in Figure 2, prisms determine the largest amount of prism-induced convergence that damps nystagmus without creating diplopia.
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FIG 5. Chin elevation and vertical Kestenbaum-type surgery. Chin elevation ≥40° both monocular and binocular (A-C). D, After surgery, which consited of a 7-mm recession of both inferior rectus muscles plus a 6-mm resection of both superior rectus muscles. Abnormal head posture has been eliminated, and the patient can look through the optical center of the spectacles.
FIG 6. Each closed square denotes the amount of abnormal head posture in degrees in an individual patient before surgery, and each closed triangle denotes the amount after surgery to correct the abnormal vertical head posture. Top, Chin elevation was ≥30° in all patients. Preoperative mean value was 40.3°; postoperative mean value was 7°(correction = 33.3°). The quantity of surgery had a mean value of 8 mm on each muscle. A rough approximation is that 1 mm of surgery corrects a 4.2° vertical head rotation. Bottom, Chin depression had a mean value of 24.5° before surgery and 2.5° after surgery (mean correction = 20.3°). The quantity of surgery had a mean value of 5.8 mm on each muscle; 1 mm corrects approximatively 3.7° of chin depression.
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FIG 7. Right head tilt with left cycloversion. An opposing right cycloversion may be obtained by creating excyclotorsion of the right eye and incyclotorsion of the left eye. This may be obtained by (1) recess-resect of the oblique muscles28; (2) surgery on the 4 cyclovertical muscles30: recession of the right superior oblique muscle and adjustable suture recession of the right superior rectus muscle (both incyclotortors), and recession of the left inferior oblique muscle and adjustable suture recession of the left inferior rectus muscle (both excyclotortors); (3) slanting of the 4 rectus muscles31: an oblique recession of 7 mm of the superior fibers of the medial rectus muscle, the nasal fibers of the inferior rectus muscle, the inferior fibers of the lateral rectus muscle, and the temporal fibers of the superior rectus muscle creates incyclotorsion. Conjugate slanting of the rectus muscles in the other eye creates excyclotorsion; (4) horizontal transposition of the vertical rectus muscle tendon.32 This transposition may be extended to any rectus muscle, depicted here as also involving horizontal rectus muscles; and (5) horizontal transposition of the vertical rectus muscle tendons.32 This transposition may be extended to any rectus muscle.
The distribution of the prisms between the 2 eyes must also be evaluated. A head turn reversal may occur when unilateral prisms are used. This is a sign of an underlying alternating headturn. At this point we know (1) the patient’s visual acuity in different conditions of fixation and (2) the nystagmus behavior in the same conditions of fixation. We have established whether we are dealing with congenital nystagmus or with manifest/latent nystagmus, what the compensatory mechanisms are, if any, and what their intensity is. We are ready to plan surgery. This surgery may be Kestenbaum-like surgery or artificial divergence surgery.
SURGERY25 Blocking Versions: The Kestenbaum-Anderson–Like Procedures Head turns require a horizontal concordant shift of the eyes. This is frequently referred to as a horizontal Kestenbaum or a horizontal Kestenbaum-Anderson procedure, in reference to the 2 ophthalmologists who proposed this type of surgery.2,12 It is common knowledge that in a patient with a concordant left head turn (the left eye fixing in adduction, the
right in abduction), if the eyes are steady 30° to the right, they must be surgically relocated, that is, shifted 30° to the left. An Anderson-like procedure for such a patient would consist of a supralarge recession of the right lateral rectus and left medial rectus muscles. This procedure is currently popular in Europe. A Kestenbaum procedure combines the recession of the Anderson-like procedure with resections of the antagonist muscles. With vertical abnormal head postures, the same rationale may be applied as is used for horizontal head turns. When nystagmus is absent in downward gaze, which induces chin elevation, the eyes should be surgically shifted upward by a similar amount (Figure 5). Adjustable suture surgery on both inferior rectus muscles is advisable. In a study of 82 patients, Spielmann and Spielmann26,27 found that results were satisfactory, as illustrated in Figure 6. No cyclodeviation was induced with surgery, and 1 mm of surgery corrected approximately 4° of chin depression and 3.6° of chin elevation (Figure 6). Head tilts are the consequence of a compensatory cycloversion. A right head tilt corresponds to a blocking innervation of incyclotorsion in the right eye and of excyclotorsion in the left eye (Figure 7). Surgery aims to create an
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FIG 8. Left head turn associated with left head tilt. A, Surgery was a horizontal Kestenbaum (8 mm recess/resect) associated with a downward transposition of the recessed right lateral rectus and left medial rectus muscles. B, Head posture after surgery.
excyclotorsion of the right eye and an incyclotorsion of the left eye. This type of surgery was named Rotatory or Oblique Kestenbaum by Conrad and de Decker28 who suggested rotating both eyes around the sagittal axis using recess-resect procedure on all the oblique muscles. This surgery frequently induces vertical imbalance, even if associated with anteroposition and retroposition of these muscles. Consequently, it has subsequently been modified by de Decker.29 I proposed recessions of the 4 cyclovertical muscles, using adjustable sutures on the rectus muscles, to avoid vertical imbalances.30 I subsequently adopted slanting of the rectus muscle insertions.31 Von Noorden et al32 proposed transposition of the vertical rectus muscles horizontally, which follows the same principle, but it is simpler and more efficient. It may be extended to any horizontal rectus muscle.29 Mixed cases are frequent. They may benefit from surgery that combines all of all the previously described procedures. For example, a left head turn with a left head tilt may benefit from the combination of a horizontal Kestenbaum with a transposition of the tendons as illustrated in Figure 8. Blocking Convergence and Artificial Divergence Surgery The diagnosis of blocking convergence is extremely simple. The aim of treatment is to create a supplementary convergence effort at distance that should damp the nystagmus. Obviously this effort, which is fusional and tonic in nature, is only possible in patients with good fusion. That is why a careful study of fusion must be carried out, as demonstrated in Figure 2. Artificial divergence surgery is the name given to this procedure by Cüppers and Adelstein.13 I perform bilateral medial rectus muscle recessions ranging from 5 to 13 mm depending on the predetermined amount of the prism as described above. I welcome the opportunity to use adjustable suture surgery as soon as a patient is old enough to permit that technique. Whenever I use adjustable sutures with artificial divergence surgery, I recess each medial rectus muscle 10 to 13 mm from the insertion. In young patients, the amount of recession depends on the amount of fusion found. I recommend 5 mm recesssions if
fusion is 30 PD/40 PD, 7 mm if fusion is 50 PD/60 PD, and 8 mm if fusion exceeds 60 PD. I do not favor unilateral procedures, which run the risk of creating inversion of a preexistent head turn, as may be seen with the use of unilateral prisms. In my opinion the fadenoperation, which increases the convergence effort mainly at near, is not indicated in treating these patients. Blocking convergence is frequently associated with a head turn. In such cases, artificial divergence surgery is preferable to Kestenbaum-like surgery, except in very young children who are prone to have a consecutive exotropia with artificial divergence operation, as seen in the retrospective study described below. In a retrospective study of 120 cases that I presented in 1992, I obtained orthophoria in 93 patients (77.5%).33 The results was slightly unsatisfactory in 23 of these 93 patients, because they still had a slight nystagmus in primary gaze with a small residual head turn. Eighteen patients ended up with exophoria, giving rise to pseudolatent nystagmus (no surgery was required). Only 9 patients were exotropic. These were mainly children with hypermetropia who were younger than 8 years (6 patients underwent surgery to undercorrect the divergence). The exotropia invariably occurred during the first year after surgery. Surprising as it sounds, we may consider that fusional convergence gives way rapidly to tonic convergence in more than 77% of the cases. A satisfactory postoperative residual fusional amplitude helps ensure the stability of the results. Four types of blocking convergence exist: fusional blocking convergence, blocking convergence of the near vision complex, prism-induced blocking convergence, and surgery-induced blocking convergence. Artificial divergence surgery is probably the most efficient procedure I know of for treating nystagmus. It is the only recourse in patients with alternating head turns with 2 null zones if blocking convergence is present. Age and Results Patients may benefit from surgery at any age. There is no need for early surgery in children except when they have a large torticollis and/or when deprivation nystagmus amblyopia might possibly develop. For example, this
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might occur in patients with ametropia, in particular if there is a large amount of astigmatism. In this situation a large abnormal head posture may prevent the patient from correctly looking through the optical center of the spectacles (Figure 5). Children with abnormal head postures less than or equal to 20° really do not require surgery. There may be an increase in the need for surgery after age 40 years when the patient’s neck is no longer supple and presbyopia has begun. An exception to this is if head flexion is present. It should always be treated because it causes a substantial handicap for work at near. In most patients, surgery does not improve visual acuity per se; it does not improve beyond that experienced before surgery in the compensatory abnormal head posture at distance or at near viewing. However, surgery increases the availability of this higher visual acuity and enlarges the visual field through transferring this acuity onto the primary position. “Vision” can be said to have been improved. Finally, the improvement is not only visual and cosmetic, but also social, through the decrease of the severe abnormal head postures and damping nystagmus in everyday situations.
CONCLUSION Nystagmus should not be a mystery for ophthalmologists. Electronystagmography is certainly most useful, especially in furthering our knowledge of nystagmus. However simple clinical study is the first step to any understanding of nystagmus. Ophthalmologists should be aware that they may understand a good deal about nystagmus simply by studying vision and visual acuity, something which they do in their everyday practice. Finally, I would like to stress the value of blocking convergence. It is a very powerful blocking mechanism that is easily detected during office examination. Patients with exophoria with pseudolatent congenital nystagmus are certainly a fascinating illustration of what fusional blocking convergence is, and the best argument in favor of artificial divergence surgery. References 1. Reinecke RD. Idiopathic infantile nystagmus: diagnosis and treatment. J Ped Ophthalmol Strabismus 1997;1:67-82. 2. Kestenbaum A. Clinical methods of neuro-ophthalmologic examination. New York: Grune & Stratton; 1946. 3. Noorden Von GK. Binocular vision and ocular motility: theory and management of strabismus. 5th ed. St Louis: Mosby; 1996. 4. Crone RA. The operative treatment of nystagmus. Ophthalmologica (Basel) 1971;163:15-20. 5. Blatt N. Ist guenstige Beinflussung oder gar Heilung des Nystagmus mittels lokaler cjirurgischer Intervention moeglich. Acta IV Cong Ophth Hisp 1933;4:437. 6. Muhlendyck H. The fadenoperation in the treatment of congenital nystagmus. In: Reinecke RD, editor. Strabismus. New York: Grune & Stratton; 1978. p. 235-48. 7. Limon de Brown E, Bernardelli J Corvera. Metodo debilitante para el tratamiento del nystagmus. Rev Mex Oftalm 1989;63:65-7. 8. Bietti CB, Bagolini B. Traitement médico-chirurgical du Nystagmus. Année Thérapeutique et Clinique en Ophtalmologie 1960;9:269-96.
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