(S. A. Patney: InteRyc Volume-1,Jan-Mar-2001,pp 13-23)

SHORT REVIEW ARTICLE ON STRABISMUS

CYCLOVERTICAL DEVIATIONS

Cyclovertical deviations comprise a group, which includes cases of vertical and/or torsional (latent and manifest) strabismus. However, purely vertical deviations are a rarity. So is the presence of true comitance in cases of vertical deviations. Mostly they are associated with a certain amount of horizontal deviation. When the angle is measured in 9 cardinal directions (or diagnostic positions) of gaze, a varying degree of incomitance is usually present and on studying the results of various tests one can frequently find some indication of the presence of a paretic factor. In many cases though, this may be difficult to establish.

Lyle has given very pertinent quotes by Chavasse, at the start of each chapter in his book. The one at the beginning of the chapter on vertical squint is given here, "The cyclovertical deviations have constituted, both in pathology and diagnosis, one of the most baffling of all problems which present themselves in the kaleidoscopic panorama of strabismus". It is as true today as it was when Chavasse wrote his wonderful book.

The incidence of a vertical deviation in cases of horizontal strabismus seems to be quite high. The various figures given in the literature are: 43% in 457 cases of convergent strabismus², 50% in 79 cases of esotropia³, 79% in 615 cases of horizontal strabismus⁴ and 26% in Lyle’s series of 298 cases of concomitant convergent squint¹.

The etiology depends on the type of vertical strabismus and will be discussed separately under each type.

Classification and symptomatology (clinical picture)

Vertical strabismus can be classified in various ways. Two of the most commonly used classifications, one old and the other more recent, are given here, as each is useful in a different way. Purely vertical deviations are rare. Mostly they are accompanied by a varying degree of horizontal deviation.

Earlier classifications of vertical deviations including that mentioned by Lyle¹ and advocated by Villaseca⁵, divided the vertical deviations into the following three main types:

1. Primary vertical squints due to palsy of vertically acting muscles
2. Secondary vertical squints, as a consequence of horizontal squints
3. Mixed cases

A more recent classification is the one advocated by von Noorden⁶ which is as follows:

1. Nonparalytic cyclovertical deviations

1. Concomitant Hyperdeviations
2. Dissociated vertical deviations (DVD)
3. Upshoot in adduction (Strabismus sursoadductorius)
4. Downshoot in adduction (Strabismus deorsoadductorius)

2. Vertical deviations due to mechanical factors
3. Paralytic cyclovertical deviations

Following is the description of some of the main types of cyclovertical strabismus.

1. Primary vertical strabismus (type 1 of the Vellaseca’s classification): This group consists of cases, in which the vertical deviation is the original one and the horizontal deviation, if present, comes later as a consequence to disturbance of binocular fixation and fusion. There may be a latent or a manifest deviation (intermittent or constant). It has been classified into the following 6 types:

1. Primary vertical deviation due to unilateral paresis of an elevator or a depressor:

(A) Paresis of superior oblique or superior rectus
(B) Paresis of inferior oblique or inferior rectus

2. Primary vertical deviation due to unilateral paresis of both elevators or both depressors
3. Primary vertical deviation due to bilateral paresis of the same muscle of each eye
4. Mixed or multiple paresis
5. Concomitant hypertropia
6. Dissociated vertical divergence (or alternating sursumduction)

2. Secondary vertical strabismus occurring as a consequence of horizontal heterotropia: A hyperdeviation is common in cases of esotropia as well as exotropia. There is no evidence of a vertical muscle paresis, although this fact does not rule out the possibility that vertical deviation was paretic in nature and with the passage of time the paresis has largely recovered and the deviation has become concomitant. The secondary vertical deviations have been divided into the following types by Urist⁷:

[1] Esotropia with bilateral elevation in adduction

[2] Esotropia with bilateral depression in adduction

[3] Exotropia with bilateral elevation in adduction

[4] Exotropia with bilateral depression in adduction

3. Mixed cases are difficult to diagnose and manage. They are uncommon. There may be various combinations as given below:

• There may be present two different types of primary vertical strabismus in the same case, e.g., dissociated vertical divergence and vertical muscle palsy.
• A secondary vertical deviation may occur as a consequence of secondary horizontal deviation, which in turn was consequent upon a primary paresis of vertically acting muscles.
• Two different types of vertical muscle paresis may occur in the same case leading to various combinations of muscle sequels and secondary horizontal strabismus.

Differential diagnosis of primary and secondary vertical strabismus is of utmost importance for planning proper line of management. The various points which help in differentiating between them (8 and 9) are enumerated in the table 37-1:

• A pre-existing vertical deviation in the unoperated eye could have been missed/masked.
• The masking of a vertical element may be explained in the following way: A vertical deviation caused by vertical rectus dysfunction is more marked in abduction and that caused by an oblique in adduction. Thus, a vertical element due to oblique overaction is more likely to occur in esotropia and may be masked in exotropia. When the exotropia without evident vertical deviation is overcorrected leading to consecutive esotropia, the preoperative masked vertical deviation due to oblique overaction may appear. Conversely, a masked preoperative vertical deviation due to vertical muscle dysfunction in esotropia may appear after it has been converted into exotropia by surgery (consecutive exotropia). The hypotropic eye is usually the fixing eye (even if it is the affected one) as most of the daily activities like eating, walking and reading etc. are carried out in depression.
• If the sound eye fixes and the affected eye is hypotropic, there is a pseudo-ptosis, which must be recognized for what it is, to avoid unwanted ptosis surgery. A simple test is all we need for differentiating between a true and pseudo-ptosis. The hypotropic eye with the ptosis is made to fix. In the case of a pseudo-ptosis due to hypotropia (and lid following the movement of the eye), the ptosis disappears when the eye is placed in primary position.
• It should be remembered that the affected eye is not always the deviating eye and that the muscle with dysfunction is not necessarily the paretic muscle. On the contrary, it is often the ipsilateral antagonist or the contralateral synergist¹⁰. The side of the fixing eye will determine whether it is to be the former or the latter.
• According to the first of The Four Golden Rules mentioned by Pratt- Johnson¹¹, in every case of vertical strabismus, superior oblique palsy is the cause unless proved otherwise. The other three follow in the following text.
• A paralysis of superior oblique (SO) is congenital unless proved otherwise. A congenital palsy may not cause symptoms until much later, usually middle age. However, a compensatory head posture (CHP) is usually adopted to achieve binocular single vision in straight-ahead position. Childhood photographs showing the presence of a CHP consistent with the type of the paralysis or paresis can provide the best evidence of a congenital palsy, in the absence of a history of double vision or squint. Sometimes there is a history of intermittent diplopia for years. When the deviation decompensates, the diplopia becomes more frequent or there are symptoms of strain during the use of the eyes.
• The second commonest cause of SO palsy after congenital, is trauma, usually a head injury. The head injury need not be serious involving loss of consciousness.
• If the SO palsy is not congenital (compensated or otherwise) or traumatic, a neurological cause including an intracranial lesion must be excluded.
• It is necessary to do a full ocular motility workout in every case of vertical deviations, even if it seems to be concomitant and secondary. Many a times the seemingly secondary deviation turns out to be a primary one. For instance, a case of alternating esotropia with mild bilateral upshoot in adduction would appear to be a case of primary esotropia (especially in a child) with a secondary bilateral inferior oblique overaction. After a full orthoptic check however, the Maddox chart (a chart showing the angle of deviation in 9 diagnostic positions of gaze) may reveal a bilateral superior oblique paresis indicated by an increase of the vertical component in oblique directions and/or a presence of cyclodeviation. If it is a superior oblique palsy the vertical deviation is maximum in contralaterodepression (depression of the eye in opposite direction), the field of action of the superior oblique.
• Any surgery to correct the deviation must include vertical muscles if it is a primary vertical deviation. Secondary vertical deviations do not need correction unless there are contractures. Commonly, correction of horizontal strabismus leads to the disappearance of the secondary vertical deviation.
• It is not an uncommon experience in a case of horizontal heterotropia with unilateral vertical deviation (e.g., an upshoot in adduction) to have a vertical deviation (upshoot in adduction) appear in the other eye after surgical correction. This may be due to the following factors:
• The other view that a vertically misplaced reattachment of horizontal muscles in the operated eye might have caused it does not seem to hold true. To cause a significant vertical deviation the vertical displacement of the re-insertion of the operated muscle has to be significant too¹².
• It might be a case of dissociated vertical deviation (DVD) or alternating sursumduction in which the vertical element in the unoperated eye was much less as compared to the operated eye.

Each of the following four conditions will be discussed in short.

Truly concomitant hypertropia (hyperdeviation with the same angle in all the directions of gaze as well as each eye fixing) is a very rare condition. Usually there is some amount of incomitance to be found in one direction of the gaze or the other. One must examine repeatedly to make sure.

The cause of the small concomitant hyperdeviation which is all there is to be found in these cases, is not known. Some of the possible explanations are mentioned below:

1. To start with, there might have been a paretic vertical strabismus, which partially recovered and developed comitance as the time went by, as is the rule in cases of paralytic strabismus.
2. Minor anatomic anomalies may be present causing an anomalous position of rest.
3. In yet other cases abnormal innervation may be responsible.
4. An abnormal position of rest may have been caused by the presence of some minor mechanical factors.

In many cases without symptoms or complications no treatment is required. Sometimes when the condition is giving rise to symptoms of strain or other problems the following modalities of therapy may be considered:

1. As the degree of deviation is small and the strabismus is concomitant, prismotherapy is usually sufficient to relieve the symptoms. The minimum power of the prism that controls diplopia is prescribed, distributed equally between the two eyes. The apex of the prism is placed in the direction of the vertical deviation, which means apex up (described as base down) for hypertropia and apex down (described as base up) for hypotropia.
2. Surgery may be required in some cases to correct a co-existing horizontal deviation. There is no need to operate on the vertical muscles. The small amount of the vertical deviation can be managed by vertical transposition of the horizontal muscles (while they are being recessed or resected) as follows:
1. For hypertropia: The insertions of the horizontal muscles are shifted downwards so that a depression action is added to their horizontal action.
2. For hypotropia: The insertions of the horizontal muscles are moved upwards to add an elevation action to their horizontal one.

Bielschowsky first published a detailed account of this interesting and intriguing condition in 1896 although it had been known since 1894.

Dissociated vertical deviation is a name given to a special group of cases where the main diagnostic feature is a spontaneous or precipitated (by disruption of fusion) supraduction of either eye. It can be accompanied by excycloduction (of the deviated eye), abduction (of the deviated eye) and nystagmus. Any or all these features may be present.

This condition has been given various names by different workers but it should not cause confusion, as the main signs of DVD are fairly typical. It is always the nonfixating eye that deviates upwards. When it is made to fixate the object the other eye deviates upwards. Some of the other names are as follows:

Alternating sursumduction, alternating hyperphoria or hypertropia, double hypertropia, occlusion hyperphoria or hypertropia, dissociated double hypertropia, dissociated alternating hyperphoria or hypertropia, dissociated vertical divergence and anatropia.

Most of these names do not carry the correct impression about the clinical characteristics of the condition. The terms "hyperdeviation, hyperphoria and hypertropia" should only be reserved for cases in which one (the hypertropic) eye deviates up and the other (hypotropic) eye deviates downwards when it is not fixating. In the case of DVD each eye takes turn to deviate up and it is always the nonfixating eye that deviates up. No hypotropia can be demonstrated. As already mentioned the condition can be unilateral or bilateral. Sometimes the hyperdeviation is manifest and constant in one eye and latent or intermittently manifest in the other eye. This is specially so when there is an accompanying horizontal heterotropia (esotropia or exotropia).

The etiology of this condition is not clear but the results of various studies including those of the upward movement of the deviating eye and the movement of redress with the search coil method and also the studies of saccade point the finger to an abnormal vertical vergence system. The saccades have been found to be abnormal.

Because of the uncertainty about the causative mechanism many theories have been put forward, none of them having gained universal acceptance. The theories with the maximum support are the following:

1. Bielschowsky’ s theory
2. Spielmann’s theory

  1. Bielschowsky’s theory

This theory tries to explain most of the signs observed in the cases of DVD. According to this theory the dissociated vertical deviations are caused by alternating and intermittent excitation of both subcortical centers that govern the vertical divergence. To support the theory Bielschowsky presents the examples of seasaw nystagmus and skew deviation. The main points of this theory are as follows:

• DVD results from alternating and intermittent excitation of both subcortical centers. These centers are concerned with controlling the vertical divergence.
• In the usual heterophoria and heterotropia the innervational association between the two eyes is maintained while in DVD it is intermittently suspended so that certain movements of each eyes can take place independently of the other eye.
• The unilateral cases, according to him, may result when the voluntary fixation reflex coexists with the involuntary action of one of the centers for vertical divergence.
• The fixating eye maintains primary position because the voluntary innervation to the depressors neutralizes the innervation to the elevators, which causes the updeviation.
• Bielschowsky demonstrated that when a neutral filter is held in front of one of the eyes to reduce the input to that eye progressively (by increasing the density of the neutral filter) the innervation to the elevators of this eye is abnormally increased. This is brought about by the increased effort to maintain fixation. When the innervation to the elevators is increased and the eye keeps on fixating there is a compensatory increase in the innervation to the depressors. As already mentioned, this is known as Bielschowsky’s phenomenon. This is not the only instance of simultaneous innervation of the antagonists, the other being seen during asymmetric convergence.
• It is almost certain that the impulse for the DVD to occur arises in the fixating eye. However, the site where this impulse for innervation to the elevators starts is not known.
• It is important to understand the basic nature and the difference between the two conditions, i.e., the DVD, which is innervational in origin and the hyperdeviations, which are caused by anomalous position of rest. Both, Bielschowsky and Spielmann, have stressed this point.
• Although elevation (updeviation) of the nonfixing eye is the most common feature, excycloduction and abduction (divergence) of the nonfixing eye are common, especially the former.

2. Spielmann’s theory

Spielmann put forward the view that DVD is caused by an imbalance in the binocular stimulation. This view may get support by the fact that DVD is pretty common in cases of infantile esotropia but it does not explain the occurrence of DVD in the patients with normal binocular functions.

Spielmann has supported Bielschowsky view that the impulse for the innervation to the elevators of the updeviating eye must originate in the fixating eye. In fact he proved it by showing that no updeviation of either eye is to be seen if fixation is prevented by interposing neutral filters in front of both eyes. When the filter is used in front of one eye only the characteristic elevation of the nonfixating eye is seen. This goes to show that in the case of DVD the fixation is the determining factor while in the case of heterophoria (hyperphoria) it is the fusion. When the fusion is prevented or disrupted the deviation is manifested (as the eye takes on the position of rest). As far as DVD is concerned the fusion is not the determining factor as this condition is also seen in the patients who do not have fusion.

Main clinical features of this condition are as follows:

1. Each eye deviates upwards [figure 1(a) and (b)] while the other eye is fixing and this may happen under the following circumstances:
1. When the patient is lost in thought or is daydreaming.
2. When the patient is tired or fatigued out.
3. When fusion is broken by some means like covering one eye as during a cover test.
4. When the input to the eye is reduced by interposing a neutral density filter in front of the eye.
2. Under the cover the updeviated eye may make vertical pendular movements [figure 37-1(c)].
3. When the cover is removed we see the updeviated eye moving downwards to take up fixation in the primary position. Usually this happens spontaneously [figure 37-1(d)] when the cover is removed but sometimes this movement of redress is not spontaneous but has to be induced by covering the other (fixing) eye [figure 37-1(e)].
4. On prolonged occlusion and/or dissociation the degree of deviation goes on increasing.
5. The amount of updeviation is often asymmetrical.
6. Under cover, excycloduction of the updeviated eye is common [figure 37-1(f)].
7. When the cover is removed the eye is seen to cruise downwards, incycloduct and often move medially or laterally (depending on whether there is an accompanying divergent or convergent deviation, respectively) to take up fixation in the primary position. The cycloduction can be detected by looking at the conjunctival blood vessels and the iris pattern.

 

 

8. Latent nystagmus is often present in cases of dissociated vertical deviations (DVD).
9. Sometimes excycloduction of the updeviated eye is accompanied by an incycloduction of the opposite eye. Thus if the right eye is, for the moment, updeviated and excycloducted, there is may be seen a simultaneous incycloduction of the left eye, the result being a cycloversion to the right (upper end of the vertical corneal meridian in both eyes moving to the right).
10. In occasional cases there is only a torsional deviation to be seen without any vertical or horizontal elements. The excycloduction may be manifest or latent (under cover only). During the recovery to primary position an incycloduction is seen to occur. These cases are referred to as dissociated torsional deviation (DTD).
11. In some patient one eye may have the full syndrome while the other only the DTD.
12. In some cases overaction of either the inferior oblique or the superior oblique is found. In the latter case A pattern may be present.
13. Latent nystagmus is present in 50% of cases. (NOTE: Latent nystagmus and excycloduction were not included in Bielschowsky’s origin description of this disease. Noorden advises use of the term "syndrome" for DVD.

14. Bielschowsky’s phenomenon: In cases of DVD when one eye is covered, e.g., OS, it deviates upwards under the cover [figure 37-2(a)]. If, then a neutral density filter is interposed in front of the fixing eye [OD in figure 37-2(b)] while the other is covered and updeviated under that cover, the latter moves downwards. It may even overshoot the mark and go down beyond the primary position mark [figure 37-2(c)]. When the density of the neutral filter is reduced resulting in an increase in the visual input to the fixing eye, the eye behind the cover is seen to gradually move up again [figure 37-2(d)].
15. DVD is mostly bilateral but asymmetrical.
16. DVD is mostly associated with esotropia or exotropia although there are some cases in which it is the only sign present. In such patients the binocular functions are normal.
17. In cases of infantile strabismus (esotropia and exotropia) the incidence of DVD is high although it may not be evident under the age of 2 years or later. Sometimes the DVD in such cases manifests for the first time after the surgery for horizontal heterotropia has been carried out or it may take years even after the surgery.
18. DVD has also been reported in association with Duane’s retraction syndrome (15). The relationship is not clear. It may be coincidental.
19. Suppression occurs commonly if the DVD manifests spontaneously. In such cases diplopia is rare. However, use of a red filter can manifest diplopia.
20. Measurement of angle of deviation can be done by any of the method using alternate cover test e.g., on the synoptophore or with the prism bars.
21. The diplopia test using the red filter: The red image is always seen (by the patient) below the white one, whichever eye is fixing, indicating that it belongs to the hypertropic eye. Each eye thus is shown to be hypertropic in turn (alternating sursumduction). This feature coupled with an absence of vertical muscle palsy is diagnostic of DVD. Moreover, this test can also give an idea not only of the magnitude of the updeviation but also help in measuring it by interposing the appropriate prisms to neutralize the separation between the two images.

The main differentiating points are given below in table 2:

DVD has to be differentiated from hyperphoria and hypertropia. This does not pose much difficulty as the other eye shows hypodeviation. The main difficulty arises when there is a case with bilateral overaction of inferior oblique muscles. These cases can be confused with those of dissociated vertical deviations (DVD) although a little attention to pertinent points can prevent it.