(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.

Incidence

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.

Etiology

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)
  1. Vertical deviations due to mechanical factors
  2. 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:
  2. (A) Paresis of superior oblique or superior rectus
    (B) Paresis of inferior oblique or inferior rectus

  3. Primary vertical deviation due to unilateral paresis of both elevators or both depressors
  4. Primary vertical deviation due to bilateral paresis of the same muscle of each eye
  5. Mixed or multiple paresis
  6. Concomitant hypertropia
  7. Dissociated vertical divergence (or alternating sursumduction)
  1. 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

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

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:

Table 1

  Primary vertical deviations Secondary vertical deviations
1 The angle of squint is larger The angle is smaller
2 Significant squint in PP Insignificant or absent
3 Angle increases in one of the oblique directions depending on the vertically acting muscle affected. Mainly present in lateroversion.
4 Horizontal angle does not vary in PP, elevation or depression. Horizontal deviation may vary increasing in elevation or depression.
5 A paretic vertical squint usually shows some limitation of ocular motility. Function of vertically acting muscles is normal.
6 Bielchowsky’s sign is + in SO palsy The sign is negative.
7 CHP, especially head tilt is an indication of primary vertical squint. Head tilt is absent unless adopted for esophoria or exophoria
8 The eye with congenital ocular palsy retains some function and vision Amblyopia and suppression is common in unilateral congenital ET.
9 A vertical deviation in the fixing eye is usually primary. A secondary vertical deviation is present in eye with horizontal squint
10 A marked elevation in adduction indicates primary vertical deviation. In secondary vertical deviation elevation in adduction is less marked.
11 It is more marked in oblique gaze. It is more pronounced in extreme horizontal gaze.
12 A marked upshoot in adduction usually   means SO palsy unless proved otherwise The secondary upshoot in adduction is usually mild, found in a case of long standing esotropia.
13 Other neurological disturbances like nystagmus and alternating hyperphoria (DVD) normally absent Other neurological disturbances like nystagmus and DVD much more likely to be present.
14 Presence of cyclodeviation likely Cyclodeviation normally absent
15 Surgery on horizontal muscles does not abolish the vertical deviation. Correction of horizontal squint often abolishes he vertical deviation, if no contractures present.

The main points regarding vertical deviations are:

A. Nonparalytic cyclovertical deviations according to Noorden’s classification

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

1) Concomitant hypertropia or hyperdeviations

Incidence

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.

Etiology

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.

Management of concomitant hypertropia

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.

 

2) Dissociated Vertical Deviations

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

Definition

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.

Terminology - Alternative names

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).

Etiology

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:

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.

Symptomatology and diagnosis

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.  

    cyclo1.gif (8113 bytes)

     

  9. Latent nystagmus is often present in cases of dissociated vertical deviations (DVD).
  10. 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).
  11. 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).
  12. In some patient one eye may have the full syndrome while the other only the DTD.
  13. In some cases overaction of either the inferior oblique or the superior oblique is found. In the latter case A pattern may be present.
  14. 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.

 

cyclo2.gif (8119 bytes)

  1. 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)].
  2. DVD is mostly bilateral but asymmetrical.
  3. 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.
  4. 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.
  5. DVD has also been reported in association with Duane’s retraction syndrome (15). The relationship is not clear. It may be coincidental.
  6. Suppression occurs commonly if the DVD manifests spontaneously. In such cases diplopia is rare. However, use of a red filter can manifest diplopia.
  7. 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.
  8. 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.

Differential diagnosis

The main differentiating points are given below in table 2:

Bilateral inferior oblique overaction Dissociated vertical deviations
1 Updeviation from PP, adduction or Abduction Updeviation or upshot in adduction, never in abduction
2 V-pattern is often present V pattern absent
3 SO action normal SO may overact
4 A-pattern exodeviation in downgaze may be present A-pattern absent unless DVD is associated with IO overaction
5 Pseudoparesis of contralateral SR + Absent
6 Incycloduction absent on refixation Incycloduction present on refixation
7 Latent nystagmus absent Often present
8 Bielschowsky’s phenomenon absent Bielschowsky’s phenomenon usually present
9 Saccadic velocity of refixation move-200-400 degrees/sec. Saccadic velocity of refixation movement:10-200 degrees/sec.

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.

(NOTE: The second and last part of this short review article on cyclovertical deviation will be published in InteRyc volume 2, 2001)

 

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