DVD: Dissociated Vertical Deviation Flashcards
What is DVD a part of alongside DHD and DTD?
Part of the Dissociated Strabismus Complex – DSC
What does DHD and DTD stand for?
DHD - Dissociated Horizontal Deviation
DTD - Dissociated Torsional Deviation
What is DVD?
- An anomaly that occurs on dissociation
- The eye under cover progressively elevates but returns to its original position once the cover is removed
- Extorsion and latent nystagmus may be associated features
- Often bilateral and asymmetrical that’s often greatest in the amblyopic eye
How many infantile strabismus (ET or XT) have DVD?
Found in >50% of patients
What did Cherfan et al. (2014) find about DVD?
Frequently associated with infantile ET where approximately 53% of IET have DVD
What age does DVD present in?
Presents in around 1 - 5 years of age, most commonly between 18 months - 3 years
What is DVD associated with in terms of BV?
Other sequelae of deficient BV such as fusion maldevelopment nystagmus syndrome and inferior oblique overaction
What is the aetiology of DVD?
- Not well understood, but in view of co-existence with early onset strabismus it is thought to relate to the early disruption of binocular functions
- Supported by the development of DVD in monkeys reared with induced esotropia (Das et al 2005)
What did Das et al. (2005) find out about DVD?
That disrupting early binocular functions in monkeys (reared with induced ET) leads to the development of DVD
What did Brodskey (1999) find out about the DVD aetiology?
Brodskey (1999) proposed that DVD is a dorsal light reflex in which asymmetrical visual input to the 2 eyes evokes a vertical divergence movement of the eyes.
The dorsal light reflex helps organisms orientate themselves vertically in response to light. It is suppressed in humans but can manifest as DVD when early-onset strabismus precludes normal binocular development.
What did Brodsky (2002) find out about DVD aetiology?
Brodsky (2002) reported a study supporting this which demonstrated a perceptual tilt of an object when one eye was occluded resulting in a cyclo-vertical divergence of the eyes to compensate
What did Bielchowsky theorise about DVD aetiology?
Bielschowsky’s theory – alternating and intermittent excitation of subcortical vertical divergence causes DVD
What did Guyton (2000) find out about DVD aetiology?
Possibly due to nystagmus blocking mechanism
Guyton (2000) suggested the early onset defect of binocular function produces unbalanced input to the vestibular system and results in this nystagmus. The cycloversion / vertical vergence is a mechanism to dampen the nystagmus
What did Ten Tusscher & Van Rijn (2010) find out about aetiology of DVD?
An imbalance between the cortical input and subcortical pathways (ten Tusscher & van Rijn 2010)
What are the clinical features of DVD?
- May be manifest or latent
- There are 3 components being Hyper Deviation, Abduction and Excyclotorsion
How do we detect DVD in clinic?
Detected in clinic by covering one eye while patient fixes target
Upward drift of non-fixing eye when pt fixes target with other eye
Alternating hyper deviation in either eye
When deviated eye moves down to take up fixation there is no corresponding downward movement in the contralateral (previously fixing) eye – goes against Herring’s Law
Can manifest spontaneously when pt is tired / daydreaming
May become apparent when reading smaller acuity letters BEO
Disappears with the absence of fixation (bilateral occlusion or in the dark)
Can small targets help with diagnosing DVD?
Yes - DVD may become apparent when reading smaller acuity letters BEO
When does DVD disappear?
Disappears with the absence of fixation (bilateral occlusion or in the dark)
What might we establish in a case history about DVD?
- Often associated with Infantile esotropia
- May notice intermittent elevation
What AHP might we see in DVD?
Head tilt, usually to fixing eye, common
What might we see in cover test in DVD?
-Note torsion / latent nystagmus
-Prolonged dissociation reveals maximum angle
- May be larger for distance
- A hypodeviation may initially be present
- Any component may be the largest DHD, DTD whole entity may be referred to as DSC
How do we do the cover/uncover test in DVD?
- Use occlude to cover one eye
- The eye under the cover will elevate
- Many need to dissociate for up to 15 seconds before elevation happens
- Often easier to see at distance fixation
- Spielmann occluder is useful
How would OMs look in DVD?
- All types of defects may be associated
- Care should be taken not to dissociate too much
- Inferior oblique overaction can coexist but must not be misdiagnosed
- May become manifest on versions where nose blocks one eye
- A & V patterns possible but A more common and often associated with o/a SO’s
- Abnormal monocular OKN
When might a DVD become manifest during OMs?
May become manifest on versions where nose blocks one eye
Which pattern is most common in DVD?
A & V patterns possible but A more common and often associated with o/a SO’s
What test is quite specific to DVD?
Bielschowsky Darkening Wedge Test
How do we conduct the Bielschowsky Darkening Wedge Test?
- Fixate light
- Occlude one eye (eye will elevate)
- Neutral density filter / Sbisa bar in front of other eye
- Increase filter until eye behind the cover will move down
- Remove filter & eye elevates again
- Can be done with occluder and filter reversed to observe DVD in the other eye
- Requires prolonged fixation
- May not always demonstrate DVD
Manifest DVD – Once the fixating eye is covered, the deviated eye shows a downward movement to take up the fixation
What is the Bielschowsky Darkening Wedge Test?
A test called the Bielschowsky Darkening Wedge Test can be used to reveal and diagnose the presence of dissociated vertical deviation, although any (or no) amount of dissociative occlusion may also prompt it to occur.
The patient is asked to look at a light. One eye is covered and a filter is placed in front of the other eye. The density or opacity of this filter is gradually increased, and the behaviour of the eye under the cover (not of the eye beneath the filter) is observed. Initially, if DVD is present, the covered eye will have elevated, but as the filter opacity is increased the eye under the cover will gradually move downwards. This Bielschowsky phenomenon is present in over 50% of persons with prominent DVD, all the more if the DVD is asymmetric and amblyopia is present as well.[3]
The Bielschowsky phenomenon is also present in the horizontal plane in patients with prominent DHD (dissociated horizontal deviation).
How do we measure DVD?
- Difficult to measure due to progressive nature
- Manifest part of deviation should be measured with simultaneous PCT first
- Alternate PCT (APCT)
- Synoptophore
- Reverse Fixation Test
How do we use the Synoptophore to measure DVD?
Fixing either eye to measure the vertical component in each eye separately
How should we use APCT to measure DVD?
- No single prism will neutralise vertical refixation movement in both eyes
- Measure FRE and FLE
- Prism put in-front of non-fixing eye while it is behind occluder
- Occluder then switched to other eye
- Prism strength is adjusted until no vertical movement to refixate is seen
- Repeat fixing with other eye
- Record maximum amount of elevation with each eye
How do we do the Reversed Fixation Test in DVD? What’s it for?
The Reversed Fixation Test is for measuring DVD
- First neutralise manifest deviation with PCT
- Observe movement of fixing eye as perform alternate Cover Test to diagnose dissociated deviation
- If dissociated element present ask pt to hold the initial neutralising prism in front of deviating eye and then neutralise the dissociated movement in the other eye
- This second measure is the magnitude of the dissociated element
What do we need to differentially diagnose DVD from?
Need to differentiate DVD from IO overaction
Even in the absence of true inferior oblique overaction, an eye with latent DVD may over-elevate in adduction, because it is occluded by the nose.
Distinguishing DVD from simple overaction of the inferior oblique muscles is important, as the surgical approaches to these 2 conditions may differ.
In addition, the 2 conditions may coexist
How do we differentially diagnose DVD from IO o/a using:
- CT,
- OMs,
- Latent Nystagmus,
- Bielchowsky,
- Reversed Fixation Test and
- Velocity of Eye Movement on CT
CT:
DVD - Progressive elevation and intorsion on refixation
IO o/a - Constant degree of elevation, no intorsion
OMs:
DVD - Elevation under cover in all positions of gaze and often an A or no-pattern
IO o/a - Greatest elevation on adduction and V-pattern common
Latent Nystagmus:
DVD - Present
IO o/a - Absent
Bielschowsky:
DVD - Present
IO o/a - Absent
Reversed Fixation Test:
DVD - Elevation of fixing eye under cover when deviating eye neutralised with prism
IO o/a - No elevation of fixing eye under cover when deviating eye neutralised with prism
Velocity of Eye Movement on CT:
DVD - Slow
IO o/a - Normal
What did Maclellan (1971) find out about patterns in DVD?
- Horizontal deviation with or without vertical (0-3yrs)
- DVD becomes more marked and easily demonstrable(3-7yrs)
- If horizontal deviation reduced DVD becomes more stable. However, the eye may intermittently drift up & symptoms experienced at this stage (7yrs & upward)
When is DVD often noted?
DVD is often noted following surgery for the horizontal deviation, but still occurs if left untreated
What variations may we see in DVD?
- Dissociated Hypotropia (‘Inverse DVD’) has been described (Kraft et al 2006, Lim 2008)
- DVD in patients with intermittent exotropia (Lim et al 2008)
Had earlier onset of strabismus than those intermittent exotropias without DVD
Worse stereopsis
Smaller in magnitude
What is the management plan for DVD?
- Order refractive correction
- Treat any amblyopia
- Horizontal deviation often managed first
When would surgery be indicated in DVD?
- Indicated if DVD is frequent and persistent
- Only if deviation is greater than 6-8^
- Only reported in around 10% of cases (Helveston 1986)
- Purpose is to reduce frequency and size of manifest phase
- Restore cosmesis
- Aims to weaken the eye’s elevating force or strengthen the depressing force
What surgical procedure would we suggest in DVD?
- IO recession / myectomy
Less effective than other procedures, therefore not procedure of choice unless there’s a big IO o/a co-existing - Anterior transposition of the IO
By moving the insertion of the IO anterior to the equator it changes its force from one of elevation to one that opposes elevation - Superior rectus recession
Superior recti recessions with posterior fixation sutures
Large superior recti recessions (10-13mm) recommended if no inferior oblique o/a (more successful) - Inferior rectus resection or plication
Not very effective as a primary procedure but can be used in recurrent cases
How do we do an anterior transposition of the IO in DVD?
By moving the insertion of the IO anterior to the equator it changes its force from one of elevation to one that opposes elevation
How do we do a superior rectus recession in DVD?
- Superior recti recessions with posterior fixation sutures
- Large superior recti recessions (10-13mm) recommended if no inferior oblique o/a (more successful)
How do we do an Inferior Rectus Resection or Plication in DVD?
Not very effective as a primary procedure but can be used in recurrent cases
What is the choice of surgery dependent on in DVD?
- Whether DVD is bilateral or unilateral
- Size of DVD
- Fixation Preference
- Associated IO o/a
- Degree of asymmetry
- Presence of A-pattern with o/a SO’s
Why does surgical choice in DVD depend on whether it’s bilateral or unilateral?
- Unilateral unusual, can sometimes uncover DVD in the other eye post-op
- If truly unilateral with IO o/a then could weaken elevators but may result in restricted elevation, if no IO o/a then need to be cautious as A pattern / torsional dip can be a problem
Why would degree of asymmetry affect surgical choice in DVD?
Magoon et al (1982) recommended Sx on BEs even if v asymmetric
- Recommend symmetrical ATIO for asymmetrical DVD with bilateral IO o/a
- If no IO o/a then bilat SR recess with less done in the less affected eye if asymmetric DVD
Why would be presence of A pattern with o/a SO’s affect surgical choice in DVD?
- Present in about 30% of cases
- A pattern – posterior tenotomy of SO to weaken
- DVD – SR recessions
How does post-op management look in DVD?
Results can be disappointing long term, with recurrence of DVD
Undercorrection:
- Often some residual undercorrection initially
- Observe
- If unilateral surgery has been performed then may uncover DVD in fellow eye
Overcorrection:
- Hypotropia can occur if overcorrected
- Anti-elevation syndrome
Further management depends on symptoms
What does DHD stand for?
Dissociated Horizontal Deviation
What is DHD?
An XT that develops spontaneously / after dissociation
What are some features of DHD?
- An XT that develops spontaneously / after dissociation
- Marked asymmetry – greater angle fixing with one eye compared to the other
- Difficulty neutralising the deviation during PCT
- Positive Bielschowsky darkening wedge test
What are the differential diagnoses for DHD?
- DHD can co-exist with ET or XT
- Asymmetry and Bielschowsky help to differentiate
- Case reports of DHD developing following an increase in hypermetropic rx – resolved when rx reduced
- Incomitant strabismus – differentiated by OM testing
How do we manage DHD?
- Refraction and treat any amblyopia
- Only requires treatment if cosmetically causing concern
Surgery
- Recession of lateral rectus with or without posterior fixation suture
- Bilateral lateral rectus recession
