16 Dissociated Vertical Deviations

Susana Gamio


Dissociated vertical deviation (DVD) is a well-recognized condition that is characterized by spontaneous upward drifting of one or both eyes, which is difficult to manage and control, and often causes psychosocial concerns.

The fixation preference, the visual acuity, the presence of anomalous head posture, the incomitance of the deviation, and the symmetry of the DVD are all factors to consider when planning surgery.

The standard treatment for manifest DVD is surgery, but with current techniques the goal of having DVD fully disappear is rarely attained. Whether to perform unilateral or bilateral procedures, or symmetrical or asymmetrical surgery, is still controversial regarding the best outcome. There is no single ideal approach to correct DVD, and the wide spectrum of reported surgical techniques corroborates this assertion.

Recently, video-oculography (VOG; an exploration method to measure horizontal and vertical deviations when fixing in binocular conditions and after occluding each eye) has provided invaluable help in unmasking bilateral cases that seemed to be unilateral. 1 The bilateralism of most pseudomonocular DVD cases can be diagnosed with VOG, allowing greater predictability of treatment and the avoidance of over- and undercorrections.

We summarize here the management options for DVD, describing the most effective procedure for each case.

16 Dissociated Vertical Deviations

16.1 Introduction

Dissociated vertical veviation (DVD) is a complex oculomotor disorder described more than a century ago, whose etiology remains controversial and whose surgical management is not entirely satisfactory.

It is characterized by an intermittent, variable, and slow upward drifting of either eye (DVD), combined with extorsion (dissociated torsional deviation [DTD]) and abduction (dissociated horizontal deviation [DHD]) of the nonfixing eye. 2 ,​ 3 The downward vertical drift of the hypertropic eye takes place together with intorsion and adduction (Video 16.1). It is usually found in patients with early onset strabismus and profound sensory anomalies. These patients often have latent nystagmus (LN), head tilt, and associated oblique muscle dysfunction.

Ever since Stevens described it in 1895, 4 many authors have sought to explain the nature of DVD, and various theories have been proposed. During the last few years Guyton 5 and later Brodsky 6 renewed the controversy about the pathogenesis of this anomaly.

Diverse treatments have been attempted, but the best current expectation is to minimize the deviation or to improve its control. With conventional therapy, DVD cannot be fully eradicated.

16.2 Clinical Characteristics

Patients with DVD usually have poor fusion and suppression. 7 When DVD is controlled it is termed “latent” (only seen when the eye is covered); when it is uncontrolled it is termed “manifest” (spontaneously visible to others). 8 Manifest DVD creates a cosmetic problem, particularly during periods of inattention, fatigue, stress, or lack of concentration.

The age of onset of DVD is usually early. 9 A mean age of 9 months was documented by Stewart et al. 10 It often becomes manifest after the achievement of a horizontal alignment, so it is important to detect it before the surgical treatment of an esotropia to treat both simultaneously.

DVD is usually bilateral. 11 ,​ 12 ,​ 13 It can be symmetrical or asymmetrical, and many cases are so markedly asymmetrical that they can appear to be unilateral (Video 16.2). Very asymmetrical DVD cases are usually associated with unilateral deep amblyopia. However, amblyopia is not a necessary prerequisite for asymmetry in DVD. Despite the fact that larger DVD amplitude is usually seen in the nonfixating eye, cases with larger DVD in the fixing eye do exist and may show hypotropia of the fellow eye in binocular conditions. 14 ,​ 15 ,​ 16 ,​ 17

Video-oculography (VOG) is a technique that measures horizontal and vertical deviations during binocular viewing as well as after occluding each eye. The bilateralism of most of pseudomonocular DVD cases can be detected with VOG. A true vertical deviation added to the dissociated hypertropia explains the DVD asymmetry in many cases (Fig. 16‑1, Fig. 16‑2, Fig. 16‑3, Fig. 16‑4).

Fig. 16.1 With both eyes open. OD is the fixing eye.
Fig. 16.2 OD is occluded. OS is fixating.
Fig. 16.3 OS is occluded. OD is fixating.
Fig. 16.4 (a) Head tilt test (HTT) toward right shoulder. First row, with both eyes open: 14 Δ 10 Δ RHT. Second row, with OD occluded: 41 Δ esotropia (ET) 35 Δ RHT. Third row, with OS occluded: 28 Δ ET 10 Δ RHT. (b) HTT toward left shoulder. With both eyes open: 14 Δ ET 7 Δ RHT. With OD occluded: 21 Δ ET 24 Δ RHT. With OS occluded: 24 Δ ET. RHT, right hypertropia.

Oblique muscle dysfunction causes DVD incomitance in different gaze positions, and the presence of a true vertical deviation (hypo- or hypertropia) causes DVD asymmetry.

The nondissociated vertical tropia can be lesser or larger than the amplitude of the DVD. When the magnitude of the DVD is smaller than the nondissociated hypertropia, the hypotropic eye is never the higher eye. During cover testing, the hypotropic eye can become hypertropic if DVD is larger than the vertical tropia, or it can remain aligned if the DVD is of a similar magnitude to the vertical tropia. This situation may be erroneously interpreted as monocular DVD.

Unmasking bilateral DVD is very important when surgery is planned. Bilateral symmetrical procedures are performed for cases of symmetrical DVD, but asymmetrical DVD is more common and must be treated with asymmetrical surgery. Determining the difference in the DVD magnitude for each eye is critical to choosing the proper surgical approach in asymmetrical cases and avoiding overcorrection.

DVD can be comitant or incomitant. Incomitant DVD is differing hypertropia in different gaze positions. DVD incomitance is mainly due to oblique muscle dysfunction and, sometimes, vertical rectus asymmetry.

When DVD is associated with inferior oblique overaction (IOOA), the hypertropia is larger in adduction and a V pattern may be observed. In extreme adduction, a true hypertropia may be seen in addition to DVD. Cases with superior oblique overaction (SOOA) show larger hypertropia in abduction of the nonfixating eye than in primary position (PP) with A pattern. 18 ,​ 19

A unique feature of DVD is the response to changes in light density: a downward movement of the occluded eye when filters of increasing density (Bagolini filter bar) are placed before the fixing eye (Bielschowsky’s phenomenon). 20

The red glass test also yields unique results in these patients. Regardless of whether the red filter is placed before the right or the left eye, the patient always sees the red light below the white one. 20

Another singular behavior of DVD is evidenced by Posner’s test 21 : when occluding one eye, the eye moves upward; when occluding the contralateral eye (keeping the other eye occluded), the hypotropic eye moves upward and the hypertropic eye moves downward, becoming aligned in the vertical plane.

Patients with DVD are usually asymptomatic, but in those cases where significant hypertropia occurs spontaneously or in those with associated horizontal misalignment, surgical treatment should be considered.

DVD neither disappears nor improves over time. In 100 patients with DVD followed by Harcourt 22 for a mean of 7.3 years, no significant decrease in the magnitude of DVD was observed.

Surgical management strategies available for DVD cannot cause DVD to disappear. Achieving a latent deviation is therefore our goal.

16.3 Treatment

When DVD is controlled or only appears occasionally, we should merely strengthen fusional mechanisms and provide spectacle correction to achieve the clearest possible image in both eyes.

Surgical treatment should be considered when a significant hypertropia manifests spontaneously, when an anomalous head posture is evident, or when there is an associated horizontal misalignment.

The fixation preference, the bilateral visual acuity, the presence of anomalous head posture, the incomitance pattern of the deviation, and the symmetry of the DVD must be considered in designing a surgical plan.

16.3.1 Bilateral versus Unilateral Surgery

Most authors prefer bilateral surgery for DVD, as the unilateral approach carries a risk of overcorrection (hypotropia of the operated eye) or manifest hypertropia of the preferred eye if the patient is capable of switching fixation. 12 ,​ 23 ,​ 24

Unilateral surgery does have a role in patients with deep unilateral amblyopia, in whom the deviating eye has no chance of fixation. 25 ,​ 26

One of the following procedures can be chosen for unilateral surgery:

  • Unilateral superior rectus (SR) recession: The amount of recession must be moderate (5–6 mm) to avoid postoperative hypotropia. This technique is chosen in cases showing similar hypertropia in both side gazes or larger deviation in abduction of the hypertropic eye.

  • Unilateral inferior oblique anterior transposition (IOAT) 27 : This procedure is used in patients with greater hypertropia in adduction and IOOA. The average correction of this procedure is about 18 Δ in PP. 28

  • Unilateral inferior rectus (IR) resection or plication/tucking 29 ,​ 30 : This procedure is reserved as a second surgery in recurrent unilateral DVD. The amount of resection or plication/tucking should be no greater than 4 to 5 mm to avoid palpebral fissure changes.

16.3.2 Symmetrical versus Asymmetrical Surgery

Bilateral symmetrical procedures are indicated for bilateral and symmetrical cases of DVD.

However, asymmetrical DVD is more common, and cases with more than 6 Δ of difference between the eyes should be treated with asymmetrical techniques. The maximal amount of interocular DVD asymmetry that would allow for achievement of a good outcome without overcorrection is not known.

The amount of SR recession should not exceed 6 mm of difference between eyes. In cases with huge asymmetry it is advised to perform unilateral SR recession.

16.3.3 DVD with IOOA and V pattern

Accounting for the pattern of incomitance is essential when planning the proper procedure to correct the deviation in all gazes.

IOAT is an excellent procedure to treat DVD with concurrent IOOA, as described by Elliott and Nankin. 31 Other authors have reported efficacy of IOAT in controlling DVD and eliminating IOOA. 32 ,​ 33 ,​ 34 ,​ 35 ,​ 36

This surgical procedure is less satisfactory if performed symmetrically between the eyes in patients with asymmetrical DVD, usually resulting in persistent postoperative vertical deviation. With DVD asymmetry, unequal surgery should be performed.

Here follow several proposed surgical protocols for asymmetrical DVD 37 ,​ 38 ,​ 39 ,​ 40 ,​ 41 :

  1. Bilateral IOAT with unilateral IO recession of the more hyperdeviating eye.

  2. Graded bilateral IOAT (1–3 mm anterior or posterior to the IR muscle insertion, with the IO more anteriorly positioned in the higher eye).

  3. Bilateral IOAT + SR recession of the higher eye.

Stager et al 42 ,​ 43 proposed transposing the IO not only anteriorly but also nasally to the nasal border of the IR (anterior nasal transposition [ANT]). This technique converts the IO muscle into an intorter and tonic depressor. Later, Fard 44 studied the effect of this new procedure in cases with DVD and concluded that ANT was effective in controlling DVD, IOOA, and V pattern.

More recently, Farid 45 compared the results of IOAT and ANT in the management of DVD associated with IOOA and concluded that both surgical techniques are similar but ANT yields more statistically significant DVD correction in PP and in abduction. Postoperative hypotropia of 2 to 4 Δ, consecutive exotropia, and antielevation syndrome (AES) 46 were reported as complications of this technique.

AES is an unwanted outcome that can result from IOAT. 47 ,​ 48 It consists of contralateral IO pseudo-overaction and marked elevation deficiency greater in abduction with V or Y pattern. The presumed cause is an excessive antielevating force vector that occurs with attempted elevation in abduction. Lateral placement of the posterior (lateral) corner of the IO muscle at the time of surgery may cause substantial extorsion after surgery. 49

When an eye with AES is fixating, fixation duress and large hypertropia of the nondominant eye may be evident.

AES can be prevented by attaching the posterior fibers of the IO muscle no more than 2 mm lateral to the IR muscle insertion site. 48

16.3.4 DVD with SOOA and A Pattern

DVD, SOOA, and A pattern frequently coexist. In this group, based on the magnitude of the A pattern, the following procedures can be performed 19

  • Bilateral SR recession, when A pattern anisotropia is 14 Δ or less.

  • Bilateral SR recession + bilateral SO tenectomy, indicated in patients with A pattern measuring 15 to 20 Δ.

  • Four oblique weakening procedure, which is the best option for cases with more than 20Δ A-pattern incomitance, especially when two horizontal muscles have had previous surgery. It is beneficial to carry out the four oblique weakening procedure to avoid transforming the A pattern into V pattern and in patients with risk of anterior segment ischemia. 50 ,​ 51 ,​ 52 While it is possible to perform a simple IO recession, the IOAT is a best option to achieve a more predictable result. There are several alternatives to treat asymmetrical cases with A pattern, namely, bilateral asymmetrical SR recession, graded bilateral IOAT, or unilateral SR recession combined with the usual SO weakening technique.

In conclusion, it is crucial to take into account the size of the pattern and the amount of asymmetry when planning surgery.

16.3.5 Comitant DVD, with Good Bilateral Visual Acuity, without Oblique Muscle Dysfunction

Large SR recession with or without hang-back technique is one of the most-used procedures in these cases 23 ,​ 53 (Video 16.3). The advantages of this procedure are that it can solve asymmetrical cases, that it is technically easy to perform, and that it has few complications. Fig. 16‑5, Fig. 16‑6, and Fig. 16‑7 show a patient with symmetrical DVD receiving symmetrical SR recession.

Fig. 16.5 Symmetrical dissociated vertical deviation. Both eyes open, without occlusion.
Fig. 16.6 OD is occluded. OS is fixating.
Fig. 16.7 OS is occluded. OD is fixating.

Posterior dissection is required to clean attachments between the SR and the levator muscle to avoid eyelid retraction and lid fissure asymmetry.

The SO tendon attaches to the undersurface of the SR muscle via the “frenulum.” When the SR muscle is recessed, an intact frenulum could cause the SO tendon to shift posteriorly with the SR muscle. If the frenulum is divided as the SR is recessed, the SO tendon will not retract and can scar to the SR muscle insertion. Kushner 54 warned that separating this connection between the SR muscle and the SO tendon could predispose the patient to SO tendon incarceration syndrome, particularly because a recession of approximately 10 mm would place the new insertion directly over the SO tendon.

The amount of SR recession depends on the size of the hypertropia, and the recession can be done asymmetrically when the magnitude of the hypertropia is different in each eye (Table 16‑1).

Table 16.1 Superior rectus recession in dissociated vertical deviation


SRR magnitude in both eyes

10 Δ ± 2.5

8 mm

15 Δ ± 2.5

10 mm

20 Δ ± 2.5

12 mm

23 Δ –25 Δ

14 mm

Abbreviation: SRR, superior rectus recession.

Source: Adapted from Prieto-Diaz J, Souza-Dias C. Estrabismo. 5th ed. Buenos Aires: Ediciones Científicas Argentinas; 2005:232.

Weakening of the SR muscle modifies the horizontal deviation in PP, causing a mean 6 Δ exodeviation, which should be taken into account when planning surgery. This procedure increases the exodeviation in patients with exotropia, especially those with V pattern, because it weakens one of the adductors in upgaze. To avoid this, the SR should be recessed and transposed nasally to minimize upgaze exodeviation.

Improvement of a direct head tilt (toward the shoulder of the fixing eye) is an added benefit of SR recession due to weakening of a PP intorter.

Large SR recession may cause limitation of elevation, but this improves over several months.

Lorenz et al 53 compared the immediate as well as the long-term effect of three different surgical procedures on DVD. The procedures were faden operation of Cüppers of the SR muscle 12 to 14 mm posterior to its insertion, faden operation of the SR muscle combined with a 3-mm recession of the muscle, and 10-mm hang-back recession of the SR muscle. The initial effect on the DVD was similar between the faden and 10-mm recession groups. However, they found the long-term effect of the faden combined with a 3-mm recession of the SR muscle to be superior.

16.4 Anomalous Head Posture

Children with DVD frequently have anomalous head posture. 55 ,​ 56 They can have head turn, as they usually fixate in adduction, but they can also have head tilts. The head tilt can be toward the shoulder of the fixating eye (direct tilt) or toward the contralateral side (inverse tilt).

Although the association between DVD and head tilt is common, there is no evidence confirming causality.

Jampolsky reported an increased hyperdeviation of the contralateral eye on head tilt to either side with the Bielschowsky head tilt test (BHTT), 57 ,​ 58 which is exactly the inverse of the behavior seen with SO palsy or SR overaction/contracture syndrome.

Direct tilt is observed in younger patients with horizontal strabismus who also adopt a head turn demanding more vestibular innervation to increase adduction, therefore facilitating monocular fixation (Fig. 16‑8). Direct tilt improves the vertical alignment when a contracture of the SR of the non fixing eye exists or in asymmetrical DVD cases in which the fixing eye has the larger DVD.

Fig. 16.8 (a–c) Direct tilt worsens vertical alignment.

Brodsky et al 56 claimed that direct tilt is not compensatory for binocular vision, while a head tilt toward the higher eye (inverse tilt) serves to neutralize the hyperdeviation and stabilize binocular vision. Most patients who adopt an inverse tilt can maintain better vertical alignment in that position (Fig. 16‑9).

Fig. 16.9 (a–e) Inverse tilt improves vertical alignment.

Guyton 59 proposed that adopting an anomalous head posture can influence LN. The head tilt would damp the LN pattern associated with the fixing eye, and therefore, surgery on the fixing eye is always necessary to abolish head tilts.

A great number of patients with DVD do not have head tilt, suggesting that other factors are playing a role.

The head tilt should be taken into account when a patient with DVD needs surgery to attempt to also improve head position.

Only gold members can continue reading. Log In or Register to continue

Stay updated, free articles. Join our Telegram channel

Feb 21, 2021 | Posted by in OPHTHALMOLOGY | Comments Off on 16 Dissociated Vertical Deviations

Full access? Get Clinical Tree

Get Clinical Tree app for offline access