DISSOCIATED VERTICAL DEVIATION COMPARED WITH INFERIOR
OBLIQUE OVERACTION
DISSOCIATED VERTICAL DEVIATION
INFERIOR OBLIQUE
OVERACTION
Present in all gaze positions
Present in adduction only
Does not obey the Hering law
Obeys the Hering law
Slow fl oating abduction, elevation,
excyclotorsion movement
Rapid elevation, abduction
movement
Not associated with A or V pattern
Often associated with V
pattern
Proportional to ambient illumination
in fi xing eye
No objective fundus torsion
Not proportional to
illumination in fi xing eye
Objective fundus
excyclotorsion
DIFFERENTIAL DIAGNOSIS OF CONGENITAL ESOTROPIA
Early-onset accommodative esotropia
Nystagmus blockage (compensation) syndrome
Möbius’ syndrome
Duane’s syndrome
Cyclic esotropia
Esotropia associated with visual loss in one eye, neurologic impairment, or
increased intracranial pressure
Strabismus fixus and other fibrosis syndromes
ACCOMMODATIVE CONVERGENCE-TO-ACCOMMODATION RATIO
CALCULATIONS
HETEROPHORIA METHOD
Determine phoria by prism and alternate cover test at optical infinity and 0.33m
distances. Control accommodation and correct acuity to 20/30 (6/9) using least plus
lens.
where
AC/A = accommodative convergence to accommodation
IPD = interpupillary distance
Δ1 = distance phoria
Δ2 = near phoria (eso is +, exo is –)
F = near fixation distance in diopters of vergence
Example:
GRADIENT METHOD
Determine phoria by prism and alternate cover test at a fixed distance, generally
0.33m. Control accommodation and correct acuity to 20/30 (6/9) with least plus
lens. Vary lens power held before eyes and remeasure alignment.
δ1 = original phoria in diopters
δ2 = new phoria with new lens
D = power of lens
Example:
ADVANTAGES AND DISADVANTAGES OF SYMMETRICAL AND
ASYMMETRICAL SURGERY
Advantages
Disadvantages
Symmetrical surgery
(recession of both lateral
recti or resection of both
medial recti)
Recessions
technically easier
than resections
Does not create lid
fissure anomalies
on side gaze
Recessions do not
sacrifice muscle
tissue
Bilateral surgery may be
difficult to explain to
patients who note
monocular strabismus
Monocular surgery lends
itself more readily to local
anesthetic techniques
Does not alter
refractive error
Asymmetrical surgery
(recession of one lateral
rectus and resection of
one medial rectus)
Preferred if one eye
deeply amblyopic
Resections involve
disposal of muscle tissue
Preferred if patient
demands surgery on
Induces plus cylinder axis
90° for 6weeks
Advantages
Disadvantages
one eye
postoperatively
Monocular surgery
lends itself more
easily to local
anesthetic
techniques
Often leads to subtle lid
tissue anomalies on side
gaze (wider in abduction
than adduction)
DIFFERENTIAL DIAGNOSIS OF OVERELEVATION IN ADDUCTION
Inferior oblique overaction
Dissociated vertical deviation
Aberrant regeneration of cranial nerve III
Rectus rotation in patients who have craniosynostosis
Tether effect in patients who have Duane’s syndrome
Tight lateral rectus muscle syndrome
POSSIBLE CAUSES OF ABDUCTION DEFICITS
CONGENITAL
ACQUIRED
Congenital esotropia
Trauma
Möbius’ syndrome[58]
Neoplasm
Duane’s syndrome
Meningitis
Congenital horizontal gaze
palsy
Hydrocephalus
Benign recurrent sixth nerve palsy [60]
[61] [62]
Pseudotumor cerebri
Gradenigo’s syndrome
Demyelinating disease
Vascular disease
Aneurysm
Postmyelography
Postimmunization
Postviral