DVD: Dissociated Vertical Deviation

Question 1

What is DVD a part of alongside DHD and DTD?

Answer 1

Part of the Dissociated Strabismus Complex – DSC

Question 2

What does DHD and DTD stand for?

Answer 2

DHD - Dissociated Horizontal Deviation

DTD - Dissociated Torsional Deviation

Question 3

What is DVD?

Answer 3

• 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

Question 4

How many infantile strabismus (ET or XT) have DVD?

Answer 4

Found in >50% of patients

Question 5

What did Cherfan et al. (2014) find about DVD?

Answer 5

Frequently associated with infantile ET where approximately 53% of IET have DVD

Question 6

What age does DVD present in?

Answer 6

Presents in around 1 - 5 years of age, most commonly between 18 months - 3 years

Question 7

What is DVD associated with in terms of BV?

Answer 7

Other sequelae of deficient BV such as fusion maldevelopment nystagmus syndrome and inferior oblique overaction

Question 8

What is the aetiology of DVD?

Answer 8

• 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)

Question 9

What did Das et al. (2005) find out about DVD?

Answer 9

That disrupting early binocular functions in monkeys (reared with induced ET) leads to the development of DVD

Question 10

What did Brodskey (1999) find out about the DVD aetiology?

Answer 10

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.

Question 11

What did Brodsky (2002) find out about DVD aetiology?

Answer 11

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

Question 12

What did Bielchowsky theorise about DVD aetiology?

Answer 12

Bielschowsky’s theory – alternating and intermittent excitation of subcortical vertical divergence causes DVD

Question 13

What did Guyton (2000) find out about DVD aetiology?

Answer 13

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

Question 14

What did Ten Tusscher & Van Rijn (2010) find out about aetiology of DVD?

Answer 14

An imbalance between the cortical input and subcortical pathways (ten Tusscher & van Rijn 2010)

Question 15

What are the clinical features of DVD?

Answer 15

• May be manifest or latent
• There are 3 components being Hyper Deviation, Abduction and Excyclotorsion

Question 16

How do we detect DVD in clinic?

Answer 16

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)

Question 17

Can small targets help with diagnosing DVD?

Answer 17

Yes - DVD may become apparent when reading smaller acuity letters BEO

Question 17

When does DVD disappear?

Answer 17

Disappears with the absence of fixation (bilateral occlusion or in the dark)

Question 18

What might we establish in a case history about DVD?

Answer 18

• Often associated with Infantile esotropia
• May notice intermittent elevation

Question 19

What AHP might we see in DVD?

Answer 19

Head tilt, usually to fixing eye, common

Question 19

What might we see in cover test in DVD?

Answer 19

-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