BASICS

DESCRIPTION

• Dissociated strabismus is an ocular deviation in which refixation of the deviated eye does not elicit an opposing deviation of the other eye (i.e., it is not a true tropia)

• Due to 3 recognizable components – vertical, horizontal, and torsional – a more appropriate designation of the condition is dissociated strabismus complex (DSC). DSC is characterized by slow elevation, abduction, and extorsion of a non-fixing eye.

• DSC can be subdivided into dissociated vertical deviation (DVD), dissociated horizontal deviation (DHD), and dissociated torsional deviation (DTD), and may have features of one or more simultaneously.

• DCS is usually comitant in all fields of gaze.

EPIDEMIOLOGY

Incidence

DVD found in 45–92% of patients with congenital/infantile esotropia.

Prevalence

Unknown

RISK FACTORS

• Congenital/infantile esotropia

• Monofixation syndrome

• Latent or manifest-latent nystagmus

• Amblyopia

Genetics

Unknown

GENERAL PREVENTION

Maintenance of alignment and correction of refractive error and amblyopia helps to promote bifoveal fixation without dissociated deviation.

PATHOPHYSIOLOGY

Generally unknown. DVD violates Hering’s law of yolk muscles. Covering one eye induces the dissociated deviation with no associated opposite deviation of the fellow eye when the dissociated eye refixates. Helveston believed that DSC resulted from maldeveloped supranuclear centers. Guyton suggested that DVD may be secondary to a cycloversion/vertical vergence produced to dampen a cyclovertical nystagmus that occurs in patients with an early onset defect of binocular function.

ETIOLOGY

Unknown

COMMONLY ASSOCIATED CONDITIONS

• Congenital/infantile esotropia

• Monofixation syndrome

• Latent or manifest-latent nystagmus

• Amblyopia

DIAGNOSIS

HISTORY

• Parents notice the eyes drifting out or up or both; often to different degrees and at different times. May be more frequent when child is ill or tired.

• It should be looked for in any case of congenital/infantile esotropia or latent or manifest-latent nystagmus.

PHYSICAL EXAM

• Deviations can be small and well controlled on one visit and large and manifest spontaneously on the next visit. The eye may be “up” one time and “out” the next time.

• The non-fixing eye is elevated, abducted, and extorted. Diplopia is not present. Bi-fixation is absent.

• The degree of each component of DSC can be documented using a +4 to +1 designation separately, with +4 being the most severe. Alternatively, use the prism cover–uncover test.

• Use the cover–uncover test or the cross-cover test. In a true hypertropia, the opposite eye is lower when the hypertropic eye is uncovered. The absence of upward refixation movements in either eye on alternate cover testing can distinguish DVD from a true hypertropia. In a true DVD, the opposite eye is never hypotropic unless the DVD is present with a true hypertropia simultaneously.

• Any of the components of DSC can be present at any examination (DHD, DTD) as well as nystagmus.

• In DVD, binocular involvement but asymmetry is the rule, with expected variability.

• DSC often coexists with true inferior oblique overaction, with or without, a “V”-pattern. DVD can simulate inferior oblique overaction by becoming manifest in adduction as the nose interrupts fixation. True vertical or horizontal deviations can also be confused with any other component of DSC.

• Prolonged patch or cover may encourage the dissociated deviation to appear

– Complete ocular examination including cycloplegic refraction

– Worth 4-dot test, Bagolini striate glasses, and Titmus or Randot stereo tests to rule out monofixation

DIFFERENTIAL DIAGNOSIS

• Inferior oblique overaction

– True hypertropia

– True exotropia

– True cyclotorsion

TREATMENT

MEDICATION

Atropine is ineffective for DSC; use only for moderate to mild associated amblyopia.

ADDITIONAL TREATMENT

General Measures

Correct refractive error and amblyopia to encourage fixation with affected eye.

SURGERY/OTHER PROCEDURES

There is no total surgical cure for any component of DSC. Options include:

• For DVD, large recessions of the superior rectus. If asymmetry exists, do unequal recessions

• For DVD, anterior transposition of the inferior oblique, especially if inferior oblique overaction exists

• For DVD, resection of the inferior oblique (less often performed)

• For DVD, Faden suture of the superior rectus

• For DHD, recession of the lateral rectus

– Correction of associated strabismus (e.g., infantile esotropia)

ONGOING CARE

FOLLOW-UP RECOMMENDATIONS

Monitor for amblyopia, recurrent deviation, and coexisting tropias.

PATIENT EDUCATION

Keep parents and family informed about the limitations of treatment including the diagnosis, treatment plan, and prognosis.

PROGNOSIS

Variable with recurrences possible. No full cure is available.

COMPLICATIONS

• Amblyopia

• Complications of strabismus surgery

ADDITIONAL READING

• Wright KW. Complex strabismus. Pediatric Ophthalmology and Strabismus, 2nd ed. Wright KW, Spiegel PH, (Eds). New York: Spinger-Verlag, 2003:450–480.

• Olitsky SE, Nelson LB. Strabismus disorders. Harley’s Pediatric Ophthalmology, 5th ed. Nelson LB, Olitsky SE, (Eds). Philadelphia: Lippincott, Williams & Wilkins, 2005:255–284.

• Wilson ME. Dissociated deviations. Strabismus Surgery, Basic and Advanced Strategies Ophthalmic Monographs 17, Plager DA (Ed). New York: Oxford University Press, 2004.

CODES

ICD9

378.9 Unspecified disorder of eye movements

CLINICAL PEARLS

• The 3 components of the DSC may all be present simultaneously or in different proportions at different times during subsequent examinations.

• Recurrence is common

• Correction of DSC in one eye may “uncover” DSC in the other eye.

• Deviations may be asymmetric between the two eyes.

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