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13 Surgical Management of Dissociated Deviations

Vertical manifestation of DD is known as DVD and is

13.1 Dissociated Deviations

characterized for being a slow, intermittent, variable, and

Dissociated deviation (DD) Represents a Challenge for

bilateral movement of elevation, abduction, and extor-

Diagnosis and Surgical Treatment. It is known to exhibit

sion of the nonfixating eye. The downward vertical drift

13

a slow, variable, and intermittent movement with vertical,

of the hypertropic eye takes place together with intorsion

horizontal, and torsional components. It is commonly

and adduction.

found in patients with early onset strabismus and pro-

The horizontal component has recently been

found sensorial anomalies [1–5].

described and is called dissociated horizontal deviation

Diagnosis is not easy because the movement is slow

(DHD) [5, 8–10]. Even though most papers consider

and needs a more prolonged occlusion to appear; the

DHD as a variable, intermittent exodeviation with a dif-

amount of deviation is variable, intermittent, and depends

ferent magnitude according to fixating eye, there exist

on attention. These patients usually show horizontal, ver-

cases that exhibit an esodeviation with the same charac-

tical, and torsional movements when performing the

teristics of variability and intermittence [11, 12]. There

cover test and have di erent amounts of deviation when

are also patients who manifest esotropia (ET) when fix-

fixing with each eye. They also have latent nystagmus

ating with one eye and exotropia (XT) when fixating

(LN), head tilt, and associated oblique muscles dysfunc-

with the other eye [9].

tion in many cases.

The torsional component of this entity, named dissoci-

A distinctive feature of dissociated strabismus is the

ated torsional deviation (DTD), occurs simultaneously

response to changes in light density; these changes impact

with vertical movement: extorsion of the elevating eye and

on the deviation amount.When neutral filters of increasing

intorsion of the fixating eye.The vertical movement always

density (bagolini filter bar) are placed before the fixating

cooccurs with extorsion of the elevating eye and intorsion

eye, the hypertropic eye falls (Bielschowsky’s phenomenon)

of the descending eye. This is influenced by oblique mus-

[6]. Conversely, increasing light in the hypertropic eye will

cles dysfunction also causing incomitance of vertical and

cause an increase in upward deviation. A further peculiar

torsional deviation in lateroversions [11, 13, 14].

behavior of patients with DD is evidenced by Posner’s

Measuring horizontal and vertical DD is complicated

maneuver [7]: when occluding one eye, the eye moves

because we need to superimpose horizontal and vertical

upwards, when occluding the contralateral eye (keeping

prisms over each eye. In addition, it is necessary to mea-

the other eye occluded), the second eye moves upwards

sure DVD and DHD with each eye fixating in all gaze posi-

and the first one downwards, becoming aligned in the ver-

tions (including head tilts) to have the necessary panorama

tical plane (Fig. 13.1).

to choose the best surgical procedure for each case.

Red glass testing yields particular results in dissoci-

Therefore, surgical treatment of patients with DD

ated vertical deviation (DVD). Regardless of whether the

requires a specific surgical approach. Long-term surgical

red filter is placed before the right eye or the left one, the

results and recommendations for these cases remain

patient sees the red light below the white one.

sparse in literature. The purpose of this chapter is to men-

These maneuvers attest to the tight interocular inter-

tion the surgical alternatives tailored to treat each partic-

relation of this particular form of strabismus.

ular case.